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	$161.65	8.566%	$175.4969	$175.50	$175.50	$175.50
Purchase #2	$237.89	11.227%	$264.5979	$264.60	$264.60	$264.60
Purchase #3	$141.70	6.255%	$150.5633	$150.56	$150.55	$150.60
Purchase #4	$83.79	6.120%	$88.9179	$88.92	$88.90	$88.90
Purchase #5	$154.29	10.698%	$170.7959	$170.80	$170.80	$170.80
Purchase #6	$163.73	4.678%	$171.3893	$171.39	$171.40	$171.40
Purchase #7	$123.69	7.142%	$132.5239	$132.52	$132.50	$132.50
7 purchase totals =	$1,066.74		$1,154.2851	$1,154.29	$1,154.25	$1,154.30