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	$82.47	10.508%	$91.1359	$91.14	$91.15	$91.10
Purchase #2	$31.83	13.605%	$36.1605	$36.16	$36.15	$36.20
Purchase #3	$98.95	9.182%	$108.0356	$108.04	$108.05	$108.00
Purchase #4	$21.49	3.726%	$22.2907	$22.29	$22.30	$22.30
Purchase #5	$178.60	10.108%	$196.6529	$196.65	$196.65	$196.70
Purchase #6	$149.97	4.414%	$156.5897	$156.59	$156.60	$156.60
Purchase #7	$75.88	3.532%	$78.5601	$78.56	$78.55	$78.60
7 purchase totals =	$639.19		$689.4254	$689.43	$689.45	$689.50