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	$139.52	8.148%	$150.8881	$150.89	$150.90	$150.90
Purchase #2	$237.91	10.478%	$262.8382	$262.84	$262.85	$262.80
Purchase #3	$237.97	11.335%	$264.9439	$264.94	$264.95	$264.90
Purchase #4	$198.93	7.272%	$213.3962	$213.40	$213.40	$213.40
Purchase #5	$74.52	10.450%	$82.3073	$82.31	$82.30	$82.30
Purchase #6	$49.83	6.592%	$53.1148	$53.11	$53.10	$53.10
Purchase #7	$65.49	5.245%	$68.925	$68.93	$68.95	$68.90
7 purchase totals =	$1,004.17		$1,096.4135	$1,096.42	$1,096.45	$1,096.30