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	$237.37	11.651%	$265.026	$265.03	$265.05	$265.00
Purchase #2	$188.89	13.501%	$214.392	$214.39	$214.40	$214.40
Purchase #3	$122.28	6.694%	$130.4654	$130.47	$130.45	$130.50
Purchase #4	$234.76	3.689%	$243.4203	$243.42	$243.40	$243.40
Purchase #5	$206.28	4.450%	$215.4595	$215.46	$215.45	$215.50
Purchase #6	$239.89	4.236%	$250.0517	$250.05	$250.05	$250.10
Purchase #7	$90.82	8.653%	$98.6787	$98.68	$98.70	$98.70
7 purchase totals =	$1,320.29		$1,417.4936	$1,417.50	$1,417.50	$1,417.60