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	$127.66	10.572%	$141.1562	$141.16	$141.15	$141.20
Purchase #2	$18.72	3.129%	$19.3057	$19.31	$19.30	$19.30
Purchase #3	$119.34	12.485%	$134.2396	$134.24	$134.25	$134.20
Purchase #4	$54.90	11.173%	$61.034	$61.03	$61.05	$61.00
Purchase #5	$37.25	13.788%	$42.386	$42.39	$42.40	$42.40
Purchase #6	$106.62	6.794%	$113.8638	$113.86	$113.85	$113.90
Purchase #7	$240.43	9.792%	$263.9729	$263.97	$263.95	$264.00
7 purchase totals =	$704.92		$775.9582	$775.96	$775.95	$776.00