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	$41.95	8.807%	$45.6445	$45.64	$45.65	$45.60
Purchase #2	$86.79	11.189%	$96.5009	$96.50	$96.50	$96.50
Purchase #3	$113.84	12.344%	$127.8924	$127.89	$127.90	$127.90
Purchase #4	$29.91	12.366%	$33.6087	$33.61	$33.60	$33.60
Purchase #5	$88.73	8.450%	$96.2277	$96.23	$96.25	$96.20
Purchase #6	$140.63	7.822%	$151.6301	$151.63	$151.65	$151.60
Purchase #7	$72.65	9.577%	$79.6077	$79.61	$79.60	$79.60
7 purchase totals =	$574.50		$631.1120	$631.11	$631.15	$631.00