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	$55.69	12.865%	$62.8545	$62.85	$62.85	$62.90
Purchase #2	$32.73	13.139%	$37.0304	$37.03	$37.05	$37.00
Purchase #3	$232.48	4.157%	$242.1442	$242.14	$242.15	$242.10
Purchase #4	$53.79	9.859%	$59.0932	$59.09	$59.10	$59.10
Purchase #5	$203.46	6.692%	$217.0755	$217.08	$217.10	$217.10
Purchase #6	$73.48	12.655%	$82.7789	$82.78	$82.80	$82.80
Purchase #7	$70.67	11.830%	$79.0303	$79.03	$79.05	$79.00
7 purchase totals =	$722.30		$780.0070	$780.00	$780.10	$780.00