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	$115.98	12.563%	$130.5506	$130.55	$130.55	$130.60
Purchase #2	$141.45	4.806%	$148.2481	$148.25	$148.25	$148.20
Purchase #3	$170.59	3.366%	$176.3321	$176.33	$176.35	$176.30
Purchase #4	$165.59	4.399%	$172.8743	$172.87	$172.85	$172.90
Purchase #5	$91.33	7.426%	$98.1122	$98.11	$98.10	$98.10
Purchase #6	$50.84	8.179%	$54.9982	$55.00	$55.00	$55.00
Purchase #7	$46.60	13.565%	$52.9213	$52.92	$52.90	$52.90
7 purchase totals =	$782.38		$834.0368	$834.03	$834.00	$834.00