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	$106.76	13.548%	$121.2238	$121.22	$121.20	$121.20
Purchase #2	$116.81	11.118%	$129.7969	$129.80	$129.80	$129.80
Purchase #3	$213.91	4.633%	$223.8205	$223.82	$223.80	$223.80
Purchase #4	$98.74	6.854%	$105.5076	$105.51	$105.50	$105.50
Purchase #5	$245.56	3.576%	$254.3412	$254.34	$254.35	$254.30
Purchase #6	$139.59	10.709%	$154.5387	$154.54	$154.55	$154.50
Purchase #7	$42.80	5.791%	$45.2785	$45.28	$45.30	$45.30
7 purchase totals =	$964.17		$1,034.5072	$1,034.51	$1,034.50	$1,034.40