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	$222.57	3.114%	$229.5008	$229.50	$229.50	$229.50
Purchase #2	$179.61	9.255%	$196.2329	$196.23	$196.25	$196.20
Purchase #3	$6.99	13.157%	$7.9097	$7.91	$7.90	$7.90
Purchase #4	$247.89	12.241%	$278.2342	$278.23	$278.25	$278.20
Purchase #5	$144.86	4.787%	$151.7944	$151.79	$151.80	$151.80
Purchase #6	$224.97	8.712%	$244.5694	$244.57	$244.55	$244.60
Purchase #7	$246.29	7.324%	$264.3283	$264.33	$264.35	$264.30
7 purchase totals =	$1,273.18		$1,372.5697	$1,372.56	$1,372.60	$1,372.50