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	$45.27	3.432%	$46.8237	$46.82	$46.80	$46.80
Purchase #2	$233.35	4.538%	$243.9394	$243.94	$243.95	$243.90
Purchase #3	$64.72	13.267%	$73.3064	$73.31	$73.30	$73.30
Purchase #4	$212.98	9.624%	$233.4772	$233.48	$233.50	$233.50
Purchase #5	$62.41	10.146%	$68.7421	$68.74	$68.75	$68.70
Purchase #6	$79.25	12.452%	$89.1182	$89.12	$89.10	$89.10
Purchase #7	$250.83	10.452%	$277.0468	$277.05	$277.05	$277.00
7 purchase totals =	$948.81		$1,032.4538	$1,032.46	$1,032.45	$1,032.30