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	$48.35	11.155%	$53.7434	$53.74	$53.75	$53.70
Purchase #2	$41.64	10.601%	$46.0543	$46.05	$46.05	$46.10
Purchase #3	$111.98	5.502%	$118.1411	$118.14	$118.15	$118.10
Purchase #4	$73.92	6.399%	$78.6501	$78.65	$78.65	$78.70
Purchase #5	$211.75	4.798%	$221.9098	$221.91	$221.90	$221.90
Purchase #6	$208.75	7.236%	$223.8552	$223.86	$223.85	$223.90
Purchase #7	$221.49	4.502%	$231.4615	$231.46	$231.45	$231.50
7 purchase totals =	$917.88		$973.8154	$973.81	$973.80	$973.90