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	$198.61	12.163%	$222.7669	$222.77	$222.75	$222.80
Purchase #2	$105.35	6.107%	$111.7837	$111.78	$111.80	$111.80
Purchase #3	$38.85	8.575%	$42.1814	$42.18	$42.20	$42.20
Purchase #4	$170.79	12.415%	$191.9936	$191.99	$192.00	$192.00
Purchase #5	$175.67	9.275%	$191.9634	$191.96	$191.95	$192.00
Purchase #6	$102.26	6.240%	$108.641	$108.64	$108.65	$108.60
Purchase #7	$123.36	13.588%	$140.1222	$140.12	$140.10	$140.10
7 purchase totals =	$914.89		$1,009.4522	$1,009.44	$1,009.45	$1,009.50