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	$82.83	4.233%	$86.3362	$86.34	$86.35	$86.30
Purchase #2	$189.79	11.809%	$212.2023	$212.20	$212.20	$212.20
Purchase #3	$199.26	11.840%	$222.8524	$222.85	$222.85	$222.90
Purchase #4	$100.92	13.481%	$114.525	$114.53	$114.55	$114.50
Purchase #5	$89.76	9.562%	$98.3429	$98.34	$98.35	$98.30
Purchase #6	$209.38	5.665%	$221.2414	$221.24	$221.25	$221.20
Purchase #7	$18.65	9.242%	$20.3736	$20.37	$20.35	$20.40
7 purchase totals =	$890.59		$975.8738	$975.87	$975.90	$975.80