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	$86.98	4.459%	$90.8584	$90.86	$90.85	$90.90
Purchase #2	$183.56	9.218%	$200.4806	$200.48	$200.50	$200.50
Purchase #3	$250.27	6.456%	$266.4274	$266.43	$266.45	$266.40
Purchase #4	$99.72	10.543%	$110.2335	$110.23	$110.25	$110.20
Purchase #5	$111.61	4.640%	$116.7887	$116.79	$116.80	$116.80
Purchase #6	$161.43	12.743%	$182.001	$182.00	$182.00	$182.00
Purchase #7	$55.86	6.459%	$59.468	$59.47	$59.45	$59.50
7 purchase totals =	$949.43		$1,026.2576	$1,026.26	$1,026.30	$1,026.30