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	$84.40	6.327%	$89.74	$89.74	$89.75	$89.70
Purchase #2	$207.40	6.706%	$221.3082	$221.31	$221.30	$221.30
Purchase #3	$123.33	13.633%	$140.1436	$140.14	$140.15	$140.10
Purchase #4	$95.72	10.688%	$105.9506	$105.95	$105.95	$106.00
Purchase #5	$169.94	10.399%	$187.6121	$187.61	$187.60	$187.60
Purchase #6	$90.81	8.656%	$98.6705	$98.67	$98.65	$98.70
Purchase #7	$203.41	6.758%	$217.1564	$217.16	$217.15	$217.20
7 purchase totals =	$975.01		$1,060.5814	$1,060.58	$1,060.55	$1,060.60