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	$159.48	9.873%	$175.2255	$175.23	$175.25	$175.20
Purchase #2	$227.99	9.702%	$250.1096	$250.11	$250.10	$250.10
Purchase #3	$19.41	3.489%	$20.0872	$20.09	$20.10	$20.10
Purchase #4	$157.86	4.414%	$164.8279	$164.83	$164.85	$164.80
Purchase #5	$122.83	7.313%	$131.8126	$131.81	$131.80	$131.80
Purchase #6	$93.91	12.130%	$105.3013	$105.30	$105.30	$105.30
Purchase #7	$16.96	9.119%	$18.5066	$18.51	$18.50	$18.50
7 purchase totals =	$798.44		$865.8707	$865.88	$865.90	$865.80