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	$115.99	9.266%	$126.7376	$126.74	$126.75	$126.70
Purchase #2	$201.28	12.796%	$227.0358	$227.04	$227.05	$227.00
Purchase #3	$219.89	3.798%	$228.2414	$228.24	$228.25	$228.20
Purchase #4	$40.73	3.382%	$42.1075	$42.11	$42.10	$42.10
Purchase #5	$227.96	12.273%	$255.9375	$255.94	$255.95	$255.90
Purchase #6	$155.52	6.617%	$165.8108	$165.81	$165.80	$165.80
Purchase #7	$41.44	10.107%	$45.6283	$45.63	$45.65	$45.60
7 purchase totals =	$1,002.81		$1,091.4989	$1,091.51	$1,091.55	$1,091.30