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	$166.26	13.517%	$188.7334	$188.73	$188.75	$188.70
Purchase #2	$87.85	11.280%	$97.7595	$97.76	$97.75	$97.80
Purchase #3	$236.46	3.561%	$244.8803	$244.88	$244.90	$244.90
Purchase #4	$82.32	3.622%	$85.3016	$85.30	$85.30	$85.30
Purchase #5	$138.69	9.149%	$151.3787	$151.38	$151.40	$151.40
Purchase #6	$231.34	3.520%	$239.4832	$239.48	$239.50	$239.50
Purchase #7	$91.68	13.279%	$103.8542	$103.85	$103.85	$103.90
7 purchase totals =	$1,034.60		$1,111.3909	$1,111.38	$1,111.45	$1,111.50