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	$141.50	7.500%	$152.1125	$152.11	$152.10	$152.10
Purchase #2	$139.64	11.795%	$156.1105	$156.11	$156.10	$156.10
Purchase #3	$34.70	13.327%	$39.3245	$39.32	$39.30	$39.30
Purchase #4	$89.77	7.172%	$96.2083	$96.21	$96.20	$96.20
Purchase #5	$42.32	10.870%	$46.9202	$46.92	$46.90	$46.90
Purchase #6	$211.51	10.292%	$233.2786	$233.28	$233.30	$233.30
Purchase #7	$150.70	6.379%	$160.3132	$160.31	$160.30	$160.30
7 purchase totals =	$810.14		$884.2678	$884.26	$884.20	$884.20