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	$233.38	9.394%	$255.3037	$255.30	$255.30	$255.30
Purchase #2	$31.66	9.804%	$34.7639	$34.76	$34.75	$34.80
Purchase #3	$243.52	8.479%	$264.1681	$264.17	$264.15	$264.20
Purchase #4	$50.57	3.435%	$52.3071	$52.31	$52.30	$52.30
Purchase #5	$117.42	11.590%	$131.029	$131.03	$131.05	$131.00
Purchase #6	$200.62	13.360%	$227.4228	$227.42	$227.40	$227.40
Purchase #7	$181.34	10.126%	$199.7025	$199.70	$199.70	$199.70
7 purchase totals =	$1,058.51		$1,164.6971	$1,164.69	$1,164.65	$1,164.70