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	$198.95	11.791%	$222.4082	$222.41	$222.40	$222.40
Purchase #2	$110.88	11.349%	$123.4638	$123.46	$123.45	$123.50
Purchase #3	$16.96	4.305%	$17.6901	$17.69	$17.70	$17.70
Purchase #4	$240.45	11.609%	$268.3638	$268.36	$268.35	$268.40
Purchase #5	$233.79	9.776%	$256.6453	$256.65	$256.65	$256.60
Purchase #6	$118.82	10.859%	$131.7227	$131.72	$131.70	$131.70
Purchase #7	$124.76	5.600%	$131.7466	$131.75	$131.75	$131.70
7 purchase totals =	$1,044.61		$1,152.0405	$1,152.04	$1,152.00	$1,152.00