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	$182.83	12.330%	$205.3729	$205.37	$205.35	$205.40
Purchase #2	$97.58	7.732%	$105.1249	$105.12	$105.10	$105.10
Purchase #3	$141.93	8.198%	$153.5654	$153.57	$153.55	$153.60
Purchase #4	$165.75	13.811%	$188.6417	$188.64	$188.65	$188.60
Purchase #5	$170.76	6.551%	$181.9465	$181.95	$181.95	$181.90
Purchase #6	$35.71	4.117%	$37.1802	$37.18	$37.20	$37.20
Purchase #7	$127.48	10.240%	$140.534	$140.53	$140.55	$140.50
7 purchase totals =	$922.04		$1,012.3656	$1,012.36	$1,012.35	$1,012.30