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	$236.60	10.620%	$261.7269	$261.73	$261.75	$261.70
Purchase #2	$80.34	6.521%	$85.579	$85.58	$85.60	$85.60
Purchase #3	$115.63	5.663%	$122.1781	$122.18	$122.20	$122.20
Purchase #4	$179.54	10.506%	$198.4025	$198.40	$198.40	$198.40
Purchase #5	$31.83	10.308%	$35.111	$35.11	$35.10	$35.10
Purchase #6	$76.58	7.137%	$82.0455	$82.05	$82.05	$82.00
Purchase #7	$80.48	11.210%	$89.5018	$89.50	$89.50	$89.50
7 purchase totals =	$801.00		$874.5448	$874.55	$874.60	$874.50