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	$230.37	10.288%	$254.0705	$254.07	$254.05	$254.10
Purchase #2	$80.29	6.300%	$85.3483	$85.35	$85.35	$85.30
Purchase #3	$117.52	11.225%	$130.7116	$130.71	$130.70	$130.70
Purchase #4	$174.91	12.494%	$196.7633	$196.76	$196.75	$196.80
Purchase #5	$190.30	8.120%	$205.7524	$205.75	$205.75	$205.80
Purchase #6	$68.56	5.285%	$72.1834	$72.18	$72.20	$72.20
Purchase #7	$209.95	8.750%	$228.3206	$228.32	$228.30	$228.30
7 purchase totals =	$1,071.90		$1,173.1501	$1,173.14	$1,173.10	$1,173.20