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	$165.42	6.145%	$175.5851	$175.59	$175.60	$175.60
Purchase #2	$245.40	4.159%	$255.6062	$255.61	$255.60	$255.60
Purchase #3	$140.40	11.200%	$156.1248	$156.12	$156.10	$156.10
Purchase #4	$92.78	13.308%	$105.1272	$105.13	$105.15	$105.10
Purchase #5	$105.40	3.691%	$109.2903	$109.29	$109.30	$109.30
Purchase #6	$52.74	4.246%	$54.9793	$54.98	$55.00	$55.00
Purchase #7	$21.65	8.610%	$23.5141	$23.51	$23.50	$23.50
7 purchase totals =	$823.79		$880.2270	$880.23	$880.25	$880.20