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	$72.38	11.444%	$80.6632	$80.66	$80.65	$80.70
Purchase #2	$11.85	4.310%	$12.3607	$12.36	$12.35	$12.40
Purchase #3	$66.45	6.658%	$70.8742	$70.87	$70.85	$70.90
Purchase #4	$49.49	9.710%	$54.2955	$54.30	$54.30	$54.30
Purchase #5	$130.56	11.408%	$145.4543	$145.45	$145.45	$145.50
Purchase #6	$221.95	9.727%	$243.5391	$243.54	$243.55	$243.50
Purchase #7	$167.78	4.605%	$175.5063	$175.51	$175.50	$175.50
7 purchase totals =	$720.46		$782.6933	$782.69	$782.65	$782.80