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	$104.74	6.776%	$111.8372	$111.84	$111.85	$111.80
Purchase #2	$64.77	13.225%	$73.3358	$73.34	$73.35	$73.30
Purchase #3	$90.66	13.872%	$103.2364	$103.24	$103.25	$103.20
Purchase #4	$70.64	7.559%	$75.9797	$75.98	$76.00	$76.00
Purchase #5	$68.61	6.301%	$72.9331	$72.93	$72.95	$72.90
Purchase #6	$49.98	11.141%	$55.5483	$55.55	$55.55	$55.50
Purchase #7	$46.36	11.205%	$51.5546	$51.55	$51.55	$51.60
7 purchase totals =	$495.76		$544.4251	$544.43	$544.50	$544.30