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	$101.69	10.436%	$112.3024	$112.30	$112.30	$112.30
Purchase #2	$69.81	12.322%	$78.412	$78.41	$78.40	$78.40
Purchase #3	$88.82	13.155%	$100.5043	$100.50	$100.50	$100.50
Purchase #4	$160.55	10.129%	$176.8121	$176.81	$176.80	$176.80
Purchase #5	$27.56	3.362%	$28.4866	$28.49	$28.50	$28.50
Purchase #6	$26.69	11.609%	$29.7884	$29.79	$29.80	$29.80
Purchase #7	$223.27	7.802%	$240.6895	$240.69	$240.70	$240.70
7 purchase totals =	$698.39		$766.9953	$766.99	$767.00	$767.00