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	$20.76	7.343%	$22.2844	$22.28	$22.30	$22.30
Purchase #2	$20.80	7.446%	$22.3488	$22.35	$22.35	$22.30
Purchase #3	$42.78	9.335%	$46.7735	$46.77	$46.75	$46.80
Purchase #4	$106.36	4.490%	$111.1356	$111.14	$111.15	$111.10
Purchase #5	$194.60	9.172%	$212.4487	$212.45	$212.45	$212.40
Purchase #6	$109.77	3.306%	$113.399	$113.40	$113.40	$113.40
Purchase #7	$159.83	13.793%	$181.8754	$181.88	$181.90	$181.90
7 purchase totals =	$654.90		$710.2654	$710.27	$710.30	$710.20