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	$136.59	3.452%	$141.3051	$141.31	$141.30	$141.30
Purchase #2	$25.53	12.326%	$28.6768	$28.68	$28.70	$28.70
Purchase #3	$131.71	3.275%	$136.0235	$136.02	$136.00	$136.00
Purchase #4	$166.75	10.520%	$184.2921	$184.29	$184.30	$184.30
Purchase #5	$120.30	9.182%	$131.3459	$131.35	$131.35	$131.30
Purchase #6	$152.76	9.502%	$167.2753	$167.28	$167.30	$167.30
Purchase #7	$211.58	4.537%	$221.1794	$221.18	$221.20	$221.20
7 purchase totals =	$945.22		$1,010.0981	$1,010.11	$1,010.15	$1,010.10