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	$206.36	10.686%	$228.4116	$228.41	$228.40	$228.40
Purchase #2	$21.96	3.451%	$22.7178	$22.72	$22.70	$22.70
Purchase #3	$143.63	3.296%	$148.364	$148.36	$148.35	$148.40
Purchase #4	$141.68	6.726%	$151.2094	$151.21	$151.20	$151.20
Purchase #5	$237.63	11.268%	$264.4061	$264.41	$264.40	$264.40
Purchase #6	$7.30	6.537%	$7.7772	$7.78	$7.80	$7.80
Purchase #7	$179.31	9.731%	$196.7587	$196.76	$196.75	$196.80
7 purchase totals =	$937.87		$1,019.6448	$1,019.65	$1,019.60	$1,019.70