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	$82.79	4.718%	$86.696	$86.70	$86.70	$86.70
Purchase #2	$116.33	9.812%	$127.7443	$127.74	$127.75	$127.70
Purchase #3	$90.46	3.285%	$93.4316	$93.43	$93.45	$93.40
Purchase #4	$127.72	3.762%	$132.5248	$132.52	$132.50	$132.50
Purchase #5	$73.28	6.723%	$78.2066	$78.21	$78.20	$78.20
Purchase #6	$148.67	11.291%	$165.4563	$165.46	$165.45	$165.50
Purchase #7	$98.34	4.844%	$103.1036	$103.10	$103.10	$103.10
7 purchase totals =	$737.59		$787.1632	$787.16	$787.15	$787.10