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	$215.86	6.347%	$229.5606	$229.56	$229.55	$229.60
Purchase #2	$56.96	8.139%	$61.596	$61.60	$61.60	$61.60
Purchase #3	$170.73	12.647%	$192.3222	$192.32	$192.30	$192.30
Purchase #4	$107.73	10.376%	$118.9081	$118.91	$118.90	$118.90
Purchase #5	$139.72	10.263%	$154.0595	$154.06	$154.05	$154.10
Purchase #6	$230.27	9.237%	$251.54	$251.54	$251.55	$251.50
Purchase #7	$78.25	6.722%	$83.51	$83.51	$83.50	$83.50
7 purchase totals =	$999.52		$1,091.4964	$1,091.50	$1,091.45	$1,091.50