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	$83.52	6.417%	$88.8795	$88.88	$88.90	$88.90
Purchase #2	$228.91	6.328%	$243.3954	$243.40	$243.40	$243.40
Purchase #3	$114.65	8.715%	$124.6417	$124.64	$124.65	$124.60
Purchase #4	$52.32	8.622%	$56.831	$56.83	$56.85	$56.80
Purchase #5	$21.86	3.152%	$22.549	$22.55	$22.55	$22.50
Purchase #6	$203.91	9.640%	$223.5669	$223.57	$223.55	$223.60
Purchase #7	$245.67	4.567%	$256.8897	$256.89	$256.90	$256.90
7 purchase totals =	$950.84		$1,016.7532	$1,016.76	$1,016.80	$1,016.70