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	$41.73	6.392%	$44.3974	$44.40	$44.40	$44.40
Purchase #2	$116.32	10.479%	$128.5092	$128.51	$128.50	$128.50
Purchase #3	$51.60	11.286%	$57.4236	$57.42	$57.40	$57.40
Purchase #4	$167.96	10.534%	$185.6529	$185.65	$185.65	$185.70
Purchase #5	$224.93	7.317%	$241.3881	$241.39	$241.40	$241.40
Purchase #6	$215.39	3.599%	$223.1419	$223.14	$223.15	$223.10
Purchase #7	$43.33	4.382%	$45.2287	$45.23	$45.25	$45.20
7 purchase totals =	$861.26		$925.7418	$925.74	$925.75	$925.70