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	$248.61	13.807%	$282.9356	$282.94	$282.95	$282.90
Purchase #2	$184.59	11.744%	$206.2682	$206.27	$206.25	$206.30
Purchase #3	$200.74	4.698%	$210.1708	$210.17	$210.15	$210.20
Purchase #4	$143.93	3.477%	$148.9344	$148.93	$148.95	$148.90
Purchase #5	$64.37	4.549%	$67.2982	$67.30	$67.30	$67.30
Purchase #6	$149.72	12.412%	$168.3032	$168.30	$168.30	$168.30
Purchase #7	$113.80	11.807%	$127.2364	$127.24	$127.25	$127.20
7 purchase totals =	$1,105.76		$1,211.1468	$1,211.15	$1,211.15	$1,211.10