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	$33.75	10.550%	$37.3106	$37.31	$37.30	$37.30
Purchase #2	$173.39	3.721%	$179.8418	$179.84	$179.85	$179.80
Purchase #3	$246.53	3.758%	$255.7946	$255.79	$255.80	$255.80
Purchase #4	$149.26	10.250%	$164.5592	$164.56	$164.55	$164.60
Purchase #5	$20.57	12.667%	$23.1756	$23.18	$23.20	$23.20
Purchase #6	$54.76	8.581%	$59.459	$59.46	$59.45	$59.50
Purchase #7	$209.71	11.488%	$233.8015	$233.80	$233.80	$233.80
7 purchase totals =	$887.97		$953.9423	$953.94	$953.95	$954.00