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	$228.64	4.644%	$239.258	$239.26	$239.25	$239.30
Purchase #2	$222.42	9.538%	$243.6344	$243.63	$243.65	$243.60
Purchase #3	$180.93	10.203%	$199.3903	$199.39	$199.40	$199.40
Purchase #4	$85.40	4.873%	$89.5615	$89.56	$89.55	$89.60
Purchase #5	$141.65	8.560%	$153.7752	$153.78	$153.80	$153.80
Purchase #6	$76.68	7.650%	$82.546	$82.55	$82.55	$82.50
Purchase #7	$98.36	7.496%	$105.7331	$105.73	$105.75	$105.70
7 purchase totals =	$1,034.08		$1,113.8985	$1,113.90	$1,113.95	$1,113.90