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	$206.76	12.766%	$233.155	$233.16	$233.15	$233.20
Purchase #2	$167.98	7.231%	$180.1266	$180.13	$180.15	$180.10
Purchase #3	$98.37	10.597%	$108.7943	$108.79	$108.80	$108.80
Purchase #4	$164.67	5.677%	$174.0183	$174.02	$174.00	$174.00
Purchase #5	$197.63	12.622%	$222.5749	$222.57	$222.55	$222.60
Purchase #6	$130.60	5.154%	$137.3311	$137.33	$137.35	$137.30
Purchase #7	$162.78	6.611%	$173.5414	$173.54	$173.55	$173.50
7 purchase totals =	$1,128.79		$1,229.5416	$1,229.54	$1,229.55	$1,229.50