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	$73.62	3.751%	$76.3815	$76.38	$76.40	$76.40
Purchase #2	$172.85	10.263%	$190.5896	$190.59	$190.60	$190.60
Purchase #3	$141.60	9.796%	$155.4711	$155.47	$155.45	$155.50
Purchase #4	$245.44	10.187%	$270.443	$270.44	$270.45	$270.40
Purchase #5	$231.94	9.763%	$254.5843	$254.58	$254.60	$254.60
Purchase #6	$156.48	9.483%	$171.319	$171.32	$171.30	$171.30
Purchase #7	$225.39	12.458%	$253.4691	$253.47	$253.45	$253.50
7 purchase totals =	$1,247.32		$1,372.2576	$1,372.25	$1,372.25	$1,372.30