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	$71.49	3.753%	$74.173	$74.17	$74.15	$74.20
Purchase #2	$182.42	7.618%	$196.3168	$196.32	$196.30	$196.30
Purchase #3	$149.88	12.125%	$168.053	$168.05	$168.05	$168.10
Purchase #4	$84.52	8.809%	$91.9654	$91.97	$91.95	$92.00
Purchase #5	$247.50	8.717%	$269.0746	$269.07	$269.05	$269.10
Purchase #6	$89.46	13.457%	$101.4986	$101.50	$101.50	$101.50
Purchase #7	$111.63	6.391%	$118.7643	$118.76	$118.75	$118.80
7 purchase totals =	$936.90		$1,019.8457	$1,019.84	$1,019.75	$1,020.00