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	$67.53	7.325%	$72.4766	$72.48	$72.50	$72.50
Purchase #2	$166.94	3.567%	$172.8947	$172.89	$172.90	$172.90
Purchase #3	$127.36	9.685%	$139.6948	$139.69	$139.70	$139.70
Purchase #4	$85.71	8.601%	$93.0819	$93.08	$93.10	$93.10
Purchase #5	$219.85	10.439%	$242.8001	$242.80	$242.80	$242.80
Purchase #6	$240.92	11.608%	$268.886	$268.89	$268.90	$268.90
Purchase #7	$106.77	12.702%	$120.3319	$120.33	$120.35	$120.30
7 purchase totals =	$1,015.08		$1,110.1660	$1,110.16	$1,110.25	$1,110.20