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	$162.69	13.190%	$184.1488	$184.15	$184.15	$184.10
Purchase #2	$24.56	12.582%	$27.6501	$27.65	$27.65	$27.70
Purchase #3	$44.67	4.755%	$46.7941	$46.79	$46.80	$46.80
Purchase #4	$72.77	7.828%	$78.4664	$78.47	$78.45	$78.50
Purchase #5	$36.73	9.325%	$40.1551	$40.16	$40.15	$40.20
Purchase #6	$83.70	4.729%	$87.6582	$87.66	$87.65	$87.70
Purchase #7	$160.30	9.384%	$175.3426	$175.34	$175.35	$175.30
7 purchase totals =	$585.42		$640.2153	$640.22	$640.20	$640.30