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	$194.81	12.528%	$219.2158	$219.22	$219.20	$219.20
Purchase #2	$237.64	9.531%	$260.2895	$260.29	$260.30	$260.30
Purchase #3	$147.75	11.253%	$164.3763	$164.38	$164.40	$164.40
Purchase #4	$37.51	8.654%	$40.7561	$40.76	$40.75	$40.80
Purchase #5	$144.54	8.205%	$156.3995	$156.40	$156.40	$156.40
Purchase #6	$196.50	3.459%	$203.2969	$203.30	$203.30	$203.30
Purchase #7	$124.77	13.433%	$141.5304	$141.53	$141.55	$141.50
7 purchase totals =	$1,083.52		$1,185.8645	$1,185.88	$1,185.90	$1,185.90