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	$11.70	10.639%	$12.9448	$12.94	$12.95	$12.90
Purchase #2	$43.96	3.112%	$45.328	$45.33	$45.35	$45.30
Purchase #3	$201.94	10.241%	$222.6207	$222.62	$222.60	$222.60
Purchase #4	$143.85	11.327%	$160.1439	$160.14	$160.15	$160.10
Purchase #5	$236.85	11.744%	$264.6657	$264.67	$264.65	$264.70
Purchase #6	$202.72	12.192%	$227.4356	$227.44	$227.45	$227.40
Purchase #7	$89.56	7.364%	$96.1552	$96.16	$96.15	$96.20
7 purchase totals =	$930.58		$1,029.2939	$1,029.30	$1,029.30	$1,029.20