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	$76.61	9.104%	$83.5846	$83.58	$83.60	$83.60
Purchase #2	$57.45	13.505%	$65.2086	$65.21	$65.20	$65.20
Purchase #3	$80.56	6.106%	$85.479	$85.48	$85.50	$85.50
Purchase #4	$219.73	13.849%	$250.1604	$250.16	$250.15	$250.20
Purchase #5	$68.28	11.424%	$76.0803	$76.08	$76.10	$76.10
Purchase #6	$238.95	6.671%	$254.8904	$254.89	$254.90	$254.90
Purchase #7	$182.93	8.651%	$198.7553	$198.76	$198.75	$198.80
7 purchase totals =	$924.51		$1,014.1586	$1,014.16	$1,014.20	$1,014.30