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	$205.38	11.527%	$229.0542	$229.05	$229.05	$229.10
Purchase #2	$62.92	7.840%	$67.8529	$67.85	$67.85	$67.90
Purchase #3	$44.79	12.508%	$50.3923	$50.39	$50.40	$50.40
Purchase #4	$195.33	12.536%	$219.8166	$219.82	$219.80	$219.80
Purchase #5	$231.73	4.708%	$242.6398	$242.64	$242.65	$242.60
Purchase #6	$241.66	6.140%	$256.4979	$256.50	$256.50	$256.50
Purchase #7	$211.86	5.297%	$223.0822	$223.08	$223.10	$223.10
7 purchase totals =	$1,193.67		$1,289.3359	$1,289.33	$1,289.35	$1,289.40