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	$98.31	12.727%	$110.8219	$110.82	$110.80	$110.80
Purchase #2	$172.35	4.275%	$179.718	$179.72	$179.70	$179.70
Purchase #3	$154.27	12.861%	$174.1107	$174.11	$174.10	$174.10
Purchase #4	$41.96	8.246%	$45.42	$45.42	$45.40	$45.40
Purchase #5	$109.45	9.472%	$119.8171	$119.82	$119.80	$119.80
Purchase #6	$203.59	12.121%	$228.2671	$228.27	$228.25	$228.30
Purchase #7	$185.42	3.603%	$192.1007	$192.10	$192.10	$192.10
7 purchase totals =	$965.35		$1,050.2555	$1,050.26	$1,050.15	$1,050.20