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	$220.57	10.528%	$243.7916	$243.79	$243.80	$243.80
Purchase #2	$80.47	10.717%	$89.094	$89.09	$89.10	$89.10
Purchase #3	$170.62	12.118%	$191.2957	$191.30	$191.30	$191.30
Purchase #4	$126.31	13.158%	$142.9299	$142.93	$142.95	$142.90
Purchase #5	$41.31	4.758%	$43.2755	$43.28	$43.30	$43.30
Purchase #6	$162.71	8.365%	$176.3207	$176.32	$176.30	$176.30
Purchase #7	$121.38	9.322%	$132.695	$132.70	$132.70	$132.70
7 purchase totals =	$923.37		$1,019.4024	$1,019.41	$1,019.45	$1,019.40