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	$101.79	9.375%	$111.3328	$111.33	$111.35	$111.30
Purchase #2	$226.76	4.183%	$236.2454	$236.25	$236.25	$236.20
Purchase #3	$169.98	9.473%	$186.0822	$186.08	$186.10	$186.10
Purchase #4	$57.72	3.134%	$59.5289	$59.53	$59.55	$59.50
Purchase #5	$50.41	5.587%	$53.2264	$53.23	$53.25	$53.20
Purchase #6	$227.63	11.793%	$254.4744	$254.47	$254.45	$254.50
Purchase #7	$9.69	5.560%	$10.2288	$10.23	$10.25	$10.20
7 purchase totals =	$843.98		$911.1189	$911.12	$911.20	$911.00