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	$68.33	5.244%	$71.9132	$71.91	$71.90	$71.90
Purchase #2	$18.53	12.567%	$20.8587	$20.86	$20.85	$20.90
Purchase #3	$168.75	5.268%	$177.6398	$177.64	$177.65	$177.60
Purchase #4	$49.89	11.633%	$55.6937	$55.69	$55.70	$55.70
Purchase #5	$182.43	7.522%	$196.1524	$196.15	$196.15	$196.20
Purchase #6	$84.32	13.297%	$95.532	$95.53	$95.55	$95.50
Purchase #7	$60.67	12.627%	$68.3308	$68.33	$68.35	$68.30
7 purchase totals =	$632.92		$686.1206	$686.11	$686.15	$686.10