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	$172.37	4.459%	$180.056	$180.06	$180.05	$180.10
Purchase #2	$67.66	6.622%	$72.1404	$72.14	$72.15	$72.10
Purchase #3	$102.37	7.227%	$109.7683	$109.77	$109.75	$109.80
Purchase #4	$185.80	4.170%	$193.5479	$193.55	$193.55	$193.50
Purchase #5	$248.31	6.681%	$264.8996	$264.90	$264.90	$264.90
Purchase #6	$60.91	8.510%	$66.0934	$66.09	$66.10	$66.10
Purchase #7	$70.34	11.458%	$78.3996	$78.40	$78.40	$78.40
7 purchase totals =	$907.76		$964.9052	$964.91	$964.90	$964.90