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	$211.66	12.467%	$238.0477	$238.05	$238.05	$238.00
Purchase #2	$90.61	9.597%	$99.3058	$99.31	$99.30	$99.30
Purchase #3	$59.90	8.730%	$65.1293	$65.13	$65.15	$65.10
Purchase #4	$232.41	11.360%	$258.8118	$258.81	$258.80	$258.80
Purchase #5	$231.45	9.519%	$253.4817	$253.48	$253.50	$253.50
Purchase #6	$71.36	9.814%	$78.3633	$78.36	$78.35	$78.40
Purchase #7	$231.88	11.421%	$258.363	$258.36	$258.35	$258.40
7 purchase totals =	$1,129.27		$1,251.5026	$1,251.50	$1,251.50	$1,251.50