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	$74.88	9.725%	$82.1621	$82.16	$82.15	$82.20
Purchase #2	$216.44	4.103%	$225.3205	$225.32	$225.30	$225.30
Purchase #3	$201.32	10.707%	$222.8753	$222.88	$222.90	$222.90
Purchase #4	$169.68	8.683%	$184.4133	$184.41	$184.40	$184.40
Purchase #5	$106.74	12.751%	$120.3504	$120.35	$120.35	$120.40
Purchase #6	$238.80	10.732%	$264.428	$264.43	$264.45	$264.40
Purchase #7	$25.93	9.644%	$28.4307	$28.43	$28.45	$28.40
7 purchase totals =	$1,033.79		$1,127.9803	$1,127.98	$1,128.00	$1,128.00