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	$212.32	9.710%	$232.9363	$232.94	$232.95	$232.90
Purchase #2	$219.78	13.822%	$250.158	$250.16	$250.15	$250.20
Purchase #3	$96.58	4.461%	$100.8884	$100.89	$100.90	$100.90
Purchase #4	$149.85	7.772%	$161.4963	$161.50	$161.50	$161.50
Purchase #5	$245.69	10.498%	$271.4825	$271.48	$271.50	$271.50
Purchase #6	$230.67	13.280%	$261.303	$261.30	$261.30	$261.30
Purchase #7	$250.37	5.648%	$264.5109	$264.51	$264.50	$264.50
7 purchase totals =	$1,405.26		$1,542.7754	$1,542.78	$1,542.80	$1,542.80