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	$147.56	7.620%	$158.8041	$158.80	$158.80	$158.80
Purchase #2	$109.27	10.483%	$120.7248	$120.72	$120.70	$120.70
Purchase #3	$42.56	7.669%	$45.8239	$45.82	$45.80	$45.80
Purchase #4	$200.29	3.165%	$206.6292	$206.63	$206.65	$206.60
Purchase #5	$116.92	11.616%	$130.5014	$130.50	$130.50	$130.50
Purchase #6	$213.84	3.141%	$220.5567	$220.56	$220.55	$220.60
Purchase #7	$178.79	13.764%	$203.3987	$203.40	$203.40	$203.40
7 purchase totals =	$1,009.23		$1,086.4388	$1,086.43	$1,086.40	$1,086.40