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	$176.29	11.515%	$196.5898	$196.59	$196.60	$196.60
Purchase #2	$147.56	5.330%	$155.4249	$155.42	$155.40	$155.40
Purchase #3	$117.32	13.272%	$132.8907	$132.89	$132.90	$132.90
Purchase #4	$201.97	5.784%	$213.6519	$213.65	$213.65	$213.70
Purchase #5	$31.53	12.356%	$35.4258	$35.43	$35.45	$35.40
Purchase #6	$219.52	8.453%	$238.076	$238.08	$238.10	$238.10
Purchase #7	$201.76	7.134%	$216.1536	$216.15	$216.15	$216.20
7 purchase totals =	$1,095.95		$1,188.2127	$1,188.21	$1,188.25	$1,188.30