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	$169.31	11.127%	$188.1491	$188.15	$188.15	$188.10
Purchase #2	$105.78	3.283%	$109.2528	$109.25	$109.25	$109.30
Purchase #3	$84.77	6.360%	$90.1614	$90.16	$90.15	$90.20
Purchase #4	$228.64	10.621%	$252.9239	$252.92	$252.90	$252.90
Purchase #5	$92.77	9.463%	$101.5488	$101.55	$101.55	$101.50
Purchase #6	$134.74	3.502%	$139.4586	$139.46	$139.45	$139.50
Purchase #7	$181.25	12.780%	$204.4138	$204.41	$204.40	$204.40
7 purchase totals =	$997.26		$1,085.9084	$1,085.90	$1,085.85	$1,085.90