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	$173.91	6.581%	$185.355	$185.36	$185.35	$185.40
Purchase #2	$136.29	13.414%	$154.5719	$154.57	$154.55	$154.60
Purchase #3	$143.53	4.748%	$150.3448	$150.34	$150.35	$150.30
Purchase #4	$224.35	3.148%	$231.4125	$231.41	$231.40	$231.40
Purchase #5	$213.74	11.737%	$238.8267	$238.83	$238.85	$238.80
Purchase #6	$49.61	4.354%	$51.77	$51.77	$51.75	$51.80
Purchase #7	$65.26	4.670%	$68.3076	$68.31	$68.30	$68.30
7 purchase totals =	$1,006.69		$1,080.5885	$1,080.59	$1,080.55	$1,080.60