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	$151.82	11.536%	$169.334	$169.33	$169.35	$169.30
Purchase #2	$197.93	3.830%	$205.5107	$205.51	$205.50	$205.50
Purchase #3	$159.41	3.543%	$165.0579	$165.06	$165.05	$165.10
Purchase #4	$96.87	13.109%	$109.5687	$109.57	$109.55	$109.60
Purchase #5	$145.97	6.601%	$155.6055	$155.61	$155.60	$155.60
Purchase #6	$80.57	13.220%	$91.2214	$91.22	$91.20	$91.20
Purchase #7	$127.69	9.380%	$139.6673	$139.67	$139.65	$139.70
7 purchase totals =	$960.26		$1,035.9655	$1,035.97	$1,035.90	$1,036.00