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	$203.56	6.218%	$216.2174	$216.22	$216.20	$216.20
Purchase #2	$227.74	7.525%	$244.8774	$244.88	$244.90	$244.90
Purchase #3	$42.36	6.761%	$45.224	$45.22	$45.20	$45.20
Purchase #4	$151.43	7.275%	$162.4465	$162.45	$162.45	$162.40
Purchase #5	$243.28	4.373%	$253.9186	$253.92	$253.90	$253.90
Purchase #6	$169.98	7.544%	$182.8033	$182.80	$182.80	$182.80
Purchase #7	$34.41	4.366%	$35.9123	$35.91	$35.90	$35.90
7 purchase totals =	$1,072.76		$1,141.3995	$1,141.40	$1,141.35	$1,141.30