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	$221.71	5.165%	$233.1613	$233.16	$233.15	$233.20
Purchase #2	$90.85	5.394%	$95.7504	$95.75	$95.75	$95.80
Purchase #3	$132.44	12.650%	$149.1937	$149.19	$149.20	$149.20
Purchase #4	$245.27	6.592%	$261.4382	$261.44	$261.45	$261.40
Purchase #5	$210.64	5.860%	$222.9835	$222.98	$223.00	$223.00
Purchase #6	$78.52	9.305%	$85.8263	$85.83	$85.85	$85.80
Purchase #7	$164.80	6.489%	$175.4939	$175.49	$175.50	$175.50
7 purchase totals =	$1,144.23		$1,223.8473	$1,223.84	$1,223.90	$1,223.90