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	$166.53	11.222%	$185.218	$185.22	$185.20	$185.20
Purchase #2	$25.49	13.648%	$28.9689	$28.97	$28.95	$29.00
Purchase #3	$232.83	13.284%	$263.7591	$263.76	$263.75	$263.80
Purchase #4	$81.42	6.168%	$86.442	$86.44	$86.45	$86.40
Purchase #5	$118.27	11.208%	$131.5257	$131.53	$131.55	$131.50
Purchase #6	$204.81	10.109%	$225.5142	$225.51	$225.50	$225.50
Purchase #7	$110.46	12.402%	$124.1592	$124.16	$124.15	$124.20
7 purchase totals =	$939.81		$1,045.5871	$1,045.59	$1,045.55	$1,045.60