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	$221.73	5.744%	$234.4662	$234.47	$234.45	$234.50
Purchase #2	$92.69	6.503%	$98.7176	$98.72	$98.70	$98.70
Purchase #3	$108.29	6.628%	$115.4675	$115.47	$115.45	$115.50
Purchase #4	$152.49	13.407%	$172.9343	$172.93	$172.95	$172.90
Purchase #5	$215.79	11.152%	$239.8549	$239.85	$239.85	$239.90
Purchase #6	$155.82	6.443%	$165.8595	$165.86	$165.85	$165.90
Purchase #7	$176.88	3.345%	$182.7966	$182.80	$182.80	$182.80
7 purchase totals =	$1,123.69		$1,210.0966	$1,210.10	$1,210.05	$1,210.20