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	$69.80	6.257%	$74.1674	$74.17	$74.15	$74.20
Purchase #2	$146.80	12.154%	$164.6421	$164.64	$164.65	$164.60
Purchase #3	$245.25	12.173%	$275.1043	$275.10	$275.10	$275.10
Purchase #4	$184.73	10.476%	$204.0823	$204.08	$204.10	$204.10
Purchase #5	$52.59	3.621%	$54.4943	$54.49	$54.50	$54.50
Purchase #6	$36.40	8.521%	$39.5016	$39.50	$39.50	$39.50
Purchase #7	$249.60	9.586%	$273.5267	$273.53	$273.55	$273.50
7 purchase totals =	$985.17		$1,085.5187	$1,085.51	$1,085.55	$1,085.50