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	$8.92	13.310%	$10.1073	$10.11	$10.10	$10.10
Purchase #2	$74.46	11.450%	$82.9857	$82.99	$83.00	$83.00
Purchase #3	$32.65	4.109%	$33.9916	$33.99	$34.00	$34.00
Purchase #4	$106.94	3.852%	$111.0593	$111.06	$111.05	$111.10
Purchase #5	$162.88	5.281%	$171.4817	$171.48	$171.50	$171.50
Purchase #6	$135.77	3.479%	$140.4934	$140.49	$140.50	$140.50
Purchase #7	$72.64	12.565%	$81.7672	$81.77	$81.75	$81.80
7 purchase totals =	$594.26		$631.8862	$631.89	$631.90	$632.00