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	$129.83	11.109%	$144.2528	$144.25	$144.25	$144.30
Purchase #2	$119.67	5.794%	$126.6037	$126.60	$126.60	$126.60
Purchase #3	$110.91	3.528%	$114.8229	$114.82	$114.80	$114.80
Purchase #4	$82.30	3.684%	$85.3319	$85.33	$85.35	$85.30
Purchase #5	$159.36	13.263%	$180.4959	$180.50	$180.50	$180.50
Purchase #6	$100.53	3.141%	$103.6876	$103.69	$103.70	$103.70
Purchase #7	$174.29	8.623%	$189.319	$189.32	$189.30	$189.30
7 purchase totals =	$876.89		$944.5138	$944.51	$944.50	$944.50