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	$207.46	7.361%	$222.7311	$222.73	$222.75	$222.70
Purchase #2	$210.43	10.394%	$232.3021	$232.30	$232.30	$232.30
Purchase #3	$112.28	13.745%	$127.7129	$127.71	$127.70	$127.70
Purchase #4	$72.54	13.760%	$82.5215	$82.52	$82.50	$82.50
Purchase #5	$145.75	13.284%	$165.1114	$165.11	$165.10	$165.10
Purchase #6	$152.94	10.720%	$169.3352	$169.34	$169.35	$169.30
Purchase #7	$96.54	4.293%	$100.6845	$100.68	$100.70	$100.70
7 purchase totals =	$997.94		$1,100.3987	$1,100.39	$1,100.40	$1,100.30