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	$229.72	10.265%	$253.3008	$253.30	$253.30	$253.30
Purchase #2	$44.27	3.524%	$45.8301	$45.83	$45.85	$45.80
Purchase #3	$29.87	11.387%	$33.2713	$33.27	$33.25	$33.30
Purchase #4	$227.87	12.498%	$256.3492	$256.35	$256.35	$256.30
Purchase #5	$220.59	13.403%	$250.1557	$250.16	$250.15	$250.20
Purchase #6	$176.64	5.616%	$186.5601	$186.56	$186.55	$186.60
Purchase #7	$149.35	11.159%	$166.016	$166.02	$166.00	$166.00
7 purchase totals =	$1,078.31		$1,191.4832	$1,191.49	$1,191.45	$1,191.50