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	$191.71	12.573%	$215.8137	$215.81	$215.80	$215.80
Purchase #2	$76.86	4.805%	$80.5531	$80.55	$80.55	$80.60
Purchase #3	$96.63	3.148%	$99.6719	$99.67	$99.65	$99.70
Purchase #4	$184.52	12.795%	$208.1293	$208.13	$208.15	$208.10
Purchase #5	$83.98	12.297%	$94.307	$94.31	$94.30	$94.30
Purchase #6	$22.69	12.594%	$25.5476	$25.55	$25.55	$25.50
Purchase #7	$31.50	12.735%	$35.5115	$35.51	$35.50	$35.50
7 purchase totals =	$687.89		$759.5341	$759.53	$759.50	$759.50