Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$141.72	11.570%	$158.117	$158.12	$158.10	$158.10
Purchase #2	$190.76	12.155%	$213.9469	$213.95	$213.95	$213.90
Purchase #3	$216.43	3.306%	$223.5852	$223.59	$223.60	$223.60
Purchase #4	$174.46	12.805%	$196.7996	$196.80	$196.80	$196.80
Purchase #5	$227.45	3.459%	$235.3175	$235.32	$235.30	$235.30
Purchase #6	$173.95	12.867%	$196.3321	$196.33	$196.35	$196.30
Purchase #7	$110.91	13.114%	$125.4547	$125.45	$125.45	$125.50
7 purchase totals =	$1,235.68		$1,349.5530	$1,349.56	$1,349.55	$1,349.50