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	$27.89	11.390%	$31.0667	$31.07	$31.05	$31.10
Purchase #2	$57.58	7.374%	$61.8259	$61.83	$61.85	$61.80
Purchase #3	$67.27	13.711%	$76.4934	$76.49	$76.50	$76.50
Purchase #4	$150.86	13.532%	$171.2744	$171.27	$171.25	$171.30
Purchase #5	$11.72	8.815%	$12.7531	$12.75	$12.75	$12.80
Purchase #6	$68.52	6.697%	$73.1088	$73.11	$73.10	$73.10
Purchase #7	$191.33	4.383%	$199.716	$199.72	$199.70	$199.70
7 purchase totals =	$575.17		$626.2383	$626.24	$626.20	$626.30