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	$122.98	6.809%	$131.3537	$131.35	$131.35	$131.40
Purchase #2	$190.30	3.460%	$196.8844	$196.88	$196.90	$196.90
Purchase #3	$166.43	5.225%	$175.126	$175.13	$175.15	$175.10
Purchase #4	$26.56	7.342%	$28.51	$28.51	$28.50	$28.50
Purchase #5	$10.47	13.616%	$11.8956	$11.90	$11.90	$11.90
Purchase #6	$220.47	7.680%	$237.4021	$237.40	$237.40	$237.40
Purchase #7	$221.86	10.498%	$245.1509	$245.15	$245.15	$245.20
7 purchase totals =	$959.07		$1,026.3227	$1,026.32	$1,026.35	$1,026.40