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	$139.39	9.351%	$152.4244	$152.42	$152.40	$152.40
Purchase #2	$135.29	9.299%	$147.8706	$147.87	$147.85	$147.90
Purchase #3	$45.50	6.647%	$48.5244	$48.52	$48.50	$48.50
Purchase #4	$10.32	6.102%	$10.9497	$10.95	$10.95	$10.90
Purchase #5	$190.83	12.728%	$215.1188	$215.12	$215.10	$215.10
Purchase #6	$53.75	3.329%	$55.5393	$55.54	$55.55	$55.50
Purchase #7	$98.63	11.543%	$110.0149	$110.01	$110.00	$110.00
7 purchase totals =	$673.71		$740.4421	$740.43	$740.35	$740.30