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	$100.31	3.371%	$103.6915	$103.69	$103.70	$103.70
Purchase #2	$26.38	8.465%	$28.6131	$28.61	$28.60	$28.60
Purchase #3	$200.47	4.782%	$210.0565	$210.06	$210.05	$210.10
Purchase #4	$243.25	6.750%	$259.6694	$259.67	$259.65	$259.70
Purchase #5	$79.58	12.816%	$89.779	$89.78	$89.80	$89.80
Purchase #6	$222.88	10.119%	$245.4332	$245.43	$245.45	$245.40
Purchase #7	$117.34	10.184%	$129.2899	$129.29	$129.30	$129.30
7 purchase totals =	$990.21		$1,066.5326	$1,066.53	$1,066.55	$1,066.60