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	$21.73	4.481%	$22.7037	$22.70	$22.70	$22.70
Purchase #2	$52.56	13.120%	$59.4559	$59.46	$59.45	$59.50
Purchase #3	$138.71	6.400%	$147.5874	$147.59	$147.60	$147.60
Purchase #4	$155.32	4.769%	$162.7272	$162.73	$162.75	$162.70
Purchase #5	$67.81	10.171%	$74.707	$74.71	$74.70	$74.70
Purchase #6	$152.46	8.645%	$165.6402	$165.64	$165.65	$165.60
Purchase #7	$12.87	12.133%	$14.4315	$14.43	$14.45	$14.40
7 purchase totals =	$601.46		$647.2529	$647.26	$647.30	$647.20