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	$174.34	13.867%	$198.5157	$198.52	$198.50	$198.50
Purchase #2	$85.48	4.829%	$89.6078	$89.61	$89.60	$89.60
Purchase #3	$74.44	9.754%	$81.7009	$81.70	$81.70	$81.70
Purchase #4	$245.67	8.349%	$266.181	$266.18	$266.20	$266.20
Purchase #5	$165.94	9.627%	$181.915	$181.92	$181.90	$181.90
Purchase #6	$124.76	3.258%	$128.8247	$128.82	$128.80	$128.80
Purchase #7	$151.72	9.338%	$165.8876	$165.89	$165.90	$165.90
7 purchase totals =	$1,022.35		$1,112.6327	$1,112.64	$1,112.60	$1,112.60