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	$180.29	5.673%	$190.5179	$190.52	$190.50	$190.50
Purchase #2	$173.61	7.169%	$186.0561	$186.06	$186.05	$186.10
Purchase #3	$60.86	6.655%	$64.9102	$64.91	$64.90	$64.90
Purchase #4	$39.36	4.578%	$41.1619	$41.16	$41.15	$41.20
Purchase #5	$211.98	4.264%	$221.0188	$221.02	$221.00	$221.00
Purchase #6	$230.72	4.404%	$240.8809	$240.88	$240.90	$240.90
Purchase #7	$144.65	8.215%	$156.533	$156.53	$156.55	$156.50
7 purchase totals =	$1,041.47		$1,101.0788	$1,101.08	$1,101.05	$1,101.10