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	$57.25	4.249%	$59.6826	$59.68	$59.70	$59.70
Purchase #2	$215.50	12.448%	$242.3254	$242.33	$242.35	$242.30
Purchase #3	$133.65	6.731%	$142.646	$142.65	$142.65	$142.60
Purchase #4	$62.89	8.390%	$68.1665	$68.17	$68.15	$68.20
Purchase #5	$138.28	6.383%	$147.1064	$147.11	$147.10	$147.10
Purchase #6	$71.46	12.338%	$80.2767	$80.28	$80.30	$80.30
Purchase #7	$109.91	5.782%	$116.265	$116.27	$116.25	$116.30
7 purchase totals =	$788.94		$856.4686	$856.49	$856.50	$856.50