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	$172.29	8.548%	$187.0173	$187.02	$187.00	$187.00
Purchase #2	$59.34	10.355%	$65.4847	$65.48	$65.50	$65.50
Purchase #3	$50.96	6.326%	$54.1837	$54.18	$54.20	$54.20
Purchase #4	$40.59	13.234%	$45.9617	$45.96	$45.95	$46.00
Purchase #5	$57.54	3.530%	$59.5712	$59.57	$59.55	$59.60
Purchase #6	$112.60	9.165%	$122.9198	$122.92	$122.90	$122.90
Purchase #7	$24.96	4.850%	$26.1706	$26.17	$26.15	$26.20
7 purchase totals =	$518.28		$561.3090	$561.30	$561.25	$561.40