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	$169.61	10.727%	$187.8041	$187.80	$187.80	$187.80
Purchase #2	$79.46	3.559%	$82.288	$82.29	$82.30	$82.30
Purchase #3	$162.96	8.343%	$176.5558	$176.56	$176.55	$176.60
Purchase #4	$243.40	13.245%	$275.6383	$275.64	$275.65	$275.60
Purchase #5	$85.96	3.867%	$89.2841	$89.28	$89.30	$89.30
Purchase #6	$42.99	10.123%	$47.3419	$47.34	$47.35	$47.30
Purchase #7	$225.42	9.855%	$247.6351	$247.64	$247.65	$247.60
7 purchase totals =	$1,009.80		$1,106.5473	$1,106.55	$1,106.60	$1,106.50