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	$205.35	8.245%	$222.2811	$222.28	$222.30	$222.30
Purchase #2	$241.85	6.766%	$258.2136	$258.21	$258.20	$258.20
Purchase #3	$44.60	4.625%	$46.6628	$46.66	$46.65	$46.70
Purchase #4	$165.84	3.380%	$171.4454	$171.45	$171.45	$171.40
Purchase #5	$89.61	11.366%	$99.7951	$99.80	$99.80	$99.80
Purchase #6	$59.91	12.413%	$67.3466	$67.35	$67.35	$67.30
Purchase #7	$152.44	6.168%	$161.8425	$161.84	$161.85	$161.80
7 purchase totals =	$959.60		$1,027.5871	$1,027.59	$1,027.60	$1,027.50