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	$67.90	6.138%	$72.0677	$72.07	$72.05	$72.10
Purchase #2	$95.75	4.764%	$100.3115	$100.31	$100.30	$100.30
Purchase #3	$142.45	3.652%	$147.6523	$147.65	$147.65	$147.70
Purchase #4	$104.81	13.228%	$118.6743	$118.67	$118.65	$118.70
Purchase #5	$229.41	9.205%	$250.5272	$250.53	$250.55	$250.50
Purchase #6	$202.85	13.460%	$230.1536	$230.15	$230.15	$230.20
Purchase #7	$173.96	10.454%	$192.1458	$192.15	$192.15	$192.10
7 purchase totals =	$1,017.13		$1,111.5324	$1,111.53	$1,111.50	$1,111.60