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	$35.73	8.765%	$38.8617	$38.86	$38.85	$38.90
Purchase #2	$200.31	11.646%	$223.6381	$223.64	$223.65	$223.60
Purchase #3	$244.91	8.386%	$265.4482	$265.45	$265.45	$265.40
Purchase #4	$222.27	11.322%	$247.4354	$247.44	$247.45	$247.40
Purchase #5	$31.73	11.433%	$35.3577	$35.36	$35.35	$35.40
Purchase #6	$160.61	12.482%	$180.6573	$180.66	$180.65	$180.70
Purchase #7	$149.83	4.469%	$156.5259	$156.53	$156.55	$156.50
7 purchase totals =	$1,045.39		$1,147.9243	$1,147.94	$1,147.95	$1,147.90