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	$59.65	8.870%	$64.941	$64.94	$64.95	$64.90
Purchase #2	$219.54	8.794%	$238.8463	$238.85	$238.85	$238.80
Purchase #3	$139.56	5.551%	$147.307	$147.31	$147.30	$147.30
Purchase #4	$33.56	6.275%	$35.6659	$35.67	$35.65	$35.70
Purchase #5	$194.39	9.517%	$212.8901	$212.89	$212.90	$212.90
Purchase #6	$197.93	7.413%	$212.6026	$212.60	$212.60	$212.60
Purchase #7	$146.42	8.119%	$158.3078	$158.31	$158.30	$158.30
7 purchase totals =	$991.05		$1,070.5607	$1,070.57	$1,070.55	$1,070.50