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	$48.39	10.373%	$53.4095	$53.41	$53.40	$53.40
Purchase #2	$125.45	9.285%	$137.098	$137.10	$137.10	$137.10
Purchase #3	$30.89	6.416%	$32.8719	$32.87	$32.85	$32.90
Purchase #4	$86.90	13.634%	$98.7479	$98.75	$98.75	$98.70
Purchase #5	$198.45	9.124%	$216.5566	$216.56	$216.55	$216.60
Purchase #6	$220.94	11.295%	$245.8952	$245.90	$245.90	$245.90
Purchase #7	$214.53	12.154%	$240.604	$240.60	$240.60	$240.60
7 purchase totals =	$925.55		$1,025.1831	$1,025.19	$1,025.15	$1,025.20