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	$47.36	10.309%	$52.2423	$52.24	$52.25	$52.20
Purchase #2	$110.42	12.264%	$123.9619	$123.96	$123.95	$124.00
Purchase #3	$83.93	7.781%	$90.4606	$90.46	$90.45	$90.50
Purchase #4	$21.74	10.321%	$23.9838	$23.98	$24.00	$24.00
Purchase #5	$41.63	7.499%	$44.7518	$44.75	$44.75	$44.80
Purchase #6	$23.88	13.528%	$27.1105	$27.11	$27.10	$27.10
Purchase #7	$99.34	12.399%	$111.6572	$111.66	$111.65	$111.70
7 purchase totals =	$428.30		$474.1681	$474.16	$474.15	$474.30