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	$24.63	4.672%	$25.7807	$25.78	$25.80	$25.80
Purchase #2	$166.72	4.169%	$173.6706	$173.67	$173.65	$173.70
Purchase #3	$83.87	6.355%	$89.1999	$89.20	$89.20	$89.20
Purchase #4	$117.98	13.788%	$134.2471	$134.25	$134.25	$134.20
Purchase #5	$219.90	3.743%	$228.1309	$228.13	$228.15	$228.10
Purchase #6	$54.41	8.830%	$59.2144	$59.21	$59.20	$59.20
Purchase #7	$18.75	13.614%	$21.3026	$21.30	$21.30	$21.30
7 purchase totals =	$686.26		$731.5462	$731.54	$731.55	$731.50