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	$139.31	9.240%	$152.1822	$152.18	$152.20	$152.20
Purchase #2	$159.44	7.540%	$171.4618	$171.46	$171.45	$171.50
Purchase #3	$162.91	7.586%	$175.2684	$175.27	$175.25	$175.30
Purchase #4	$129.56	5.608%	$136.8257	$136.83	$136.85	$136.80
Purchase #5	$82.82	10.775%	$91.7439	$91.74	$91.75	$91.70
Purchase #6	$243.91	7.573%	$262.3813	$262.38	$262.40	$262.40
Purchase #7	$244.77	12.567%	$275.5302	$275.53	$275.55	$275.50
7 purchase totals =	$1,162.72		$1,265.3935	$1,265.39	$1,265.45	$1,265.40