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	$139.32	6.244%	$148.0191	$148.02	$148.00	$148.00
Purchase #2	$7.56	4.616%	$7.909	$7.91	$7.90	$7.90
Purchase #3	$242.92	3.207%	$250.7104	$250.71	$250.70	$250.70
Purchase #4	$160.43	12.156%	$179.9319	$179.93	$179.95	$179.90
Purchase #5	$196.77	4.444%	$205.5145	$205.51	$205.50	$205.50
Purchase #6	$196.79	6.521%	$209.6227	$209.62	$209.60	$209.60
Purchase #7	$152.39	11.608%	$170.0794	$170.08	$170.10	$170.10
7 purchase totals =	$1,096.18		$1,171.7870	$1,171.78	$1,171.75	$1,171.70