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	$185.30	4.594%	$193.8127	$193.81	$193.80	$193.80
Purchase #2	$249.54	6.547%	$265.8774	$265.88	$265.90	$265.90
Purchase #3	$172.75	13.778%	$196.5515	$196.55	$196.55	$196.60
Purchase #4	$191.54	10.816%	$212.257	$212.26	$212.25	$212.30
Purchase #5	$75.37	4.345%	$78.6448	$78.64	$78.65	$78.60
Purchase #6	$110.50	3.409%	$114.2669	$114.27	$114.25	$114.30
Purchase #7	$210.46	12.687%	$237.1611	$237.16	$237.15	$237.20
7 purchase totals =	$1,195.46		$1,298.5714	$1,298.57	$1,298.55	$1,298.70