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	$134.74	13.266%	$152.6146	$152.61	$152.60	$152.60
Purchase #2	$67.56	11.471%	$75.3098	$75.31	$75.30	$75.30
Purchase #3	$235.79	11.686%	$263.3444	$263.34	$263.35	$263.30
Purchase #4	$52.60	11.869%	$58.8431	$58.84	$58.85	$58.80
Purchase #5	$27.93	13.501%	$31.7008	$31.70	$31.70	$31.70
Purchase #6	$154.28	11.417%	$171.8941	$171.89	$171.90	$171.90
Purchase #7	$224.56	11.534%	$250.4608	$250.46	$250.45	$250.50
7 purchase totals =	$897.46		$1,004.1676	$1,004.15	$1,004.15	$1,004.10