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	$52.46	12.633%	$59.0873	$59.09	$59.10	$59.10
Purchase #2	$81.35	5.136%	$85.5281	$85.53	$85.55	$85.50
Purchase #3	$79.63	3.429%	$82.3605	$82.36	$82.35	$82.40
Purchase #4	$242.52	7.373%	$260.401	$260.40	$260.40	$260.40
Purchase #5	$123.30	8.760%	$134.1011	$134.10	$134.10	$134.10
Purchase #6	$226.36	7.204%	$242.667	$242.67	$242.65	$242.70
Purchase #7	$200.77	5.685%	$212.1838	$212.18	$212.20	$212.20
7 purchase totals =	$1,006.39		$1,076.3288	$1,076.33	$1,076.35	$1,076.40