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	$96.78	9.384%	$105.8618	$105.86	$105.85	$105.90
Purchase #2	$107.89	3.557%	$111.7276	$111.73	$111.75	$111.70
Purchase #3	$199.62	5.852%	$211.3018	$211.30	$211.30	$211.30
Purchase #4	$143.85	9.654%	$157.7373	$157.74	$157.75	$157.70
Purchase #5	$165.45	13.474%	$187.7427	$187.74	$187.75	$187.70
Purchase #6	$114.31	8.536%	$124.0675	$124.07	$124.05	$124.10
Purchase #7	$164.90	12.497%	$185.5076	$185.51	$185.50	$185.50
7 purchase totals =	$992.80		$1,083.9463	$1,083.95	$1,083.95	$1,083.90