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	$115.46	10.475%	$127.5544	$127.55	$127.55	$127.60
Purchase #2	$76.79	11.852%	$85.8912	$85.89	$85.90	$85.90
Purchase #3	$49.84	9.350%	$54.5	$54.50	$54.50	$54.50
Purchase #4	$6.36	3.170%	$6.5616	$6.56	$6.55	$6.60
Purchase #5	$240.45	6.691%	$256.5385	$256.54	$256.55	$256.50
Purchase #6	$162.28	8.263%	$175.6892	$175.69	$175.70	$175.70
Purchase #7	$158.41	9.663%	$173.7172	$173.72	$173.70	$173.70
7 purchase totals =	$809.59		$880.4521	$880.45	$880.45	$880.50