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	$30.89	4.660%	$32.3295	$32.33	$32.35	$32.30
Purchase #2	$64.25	4.594%	$67.2016	$67.20	$67.20	$67.20
Purchase #3	$230.47	3.486%	$238.5042	$238.50	$238.50	$238.50
Purchase #4	$219.85	13.401%	$249.3121	$249.31	$249.30	$249.30
Purchase #5	$108.52	13.524%	$123.1962	$123.20	$123.20	$123.20
Purchase #6	$99.37	7.506%	$106.8287	$106.83	$106.85	$106.80
Purchase #7	$105.40	3.579%	$109.1723	$109.17	$109.15	$109.20
7 purchase totals =	$858.75		$926.5446	$926.54	$926.55	$926.50