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	$55.42	7.600%	$59.6319	$59.63	$59.65	$59.60
Purchase #2	$152.79	6.126%	$162.1499	$162.15	$162.15	$162.10
Purchase #3	$203.59	8.214%	$220.3129	$220.31	$220.30	$220.30
Purchase #4	$220.62	11.293%	$245.5346	$245.53	$245.55	$245.50
Purchase #5	$204.82	5.817%	$216.7344	$216.73	$216.75	$216.70
Purchase #6	$91.60	7.491%	$98.4618	$98.46	$98.45	$98.50
Purchase #7	$16.50	9.592%	$18.0827	$18.08	$18.10	$18.10
7 purchase totals =	$945.34		$1,020.9082	$1,020.89	$1,020.95	$1,020.80