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	$238.55	7.240%	$255.821	$255.82	$255.80	$255.80
Purchase #2	$198.68	7.435%	$213.4519	$213.45	$213.45	$213.50
Purchase #3	$107.63	4.841%	$112.8404	$112.84	$112.85	$112.80
Purchase #4	$99.45	12.347%	$111.7291	$111.73	$111.75	$111.70
Purchase #5	$121.28	6.482%	$129.1414	$129.14	$129.15	$129.10
Purchase #6	$116.26	10.529%	$128.501	$128.50	$128.50	$128.50
Purchase #7	$99.36	12.464%	$111.7442	$111.74	$111.75	$111.70
7 purchase totals =	$981.21		$1,063.2290	$1,063.22	$1,063.25	$1,063.10