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	$75.92	9.401%	$83.0572	$83.06	$83.05	$83.10
Purchase #2	$170.59	5.228%	$179.5084	$179.51	$179.50	$179.50
Purchase #3	$7.33	7.847%	$7.9052	$7.91	$7.90	$7.90
Purchase #4	$162.90	12.394%	$183.0898	$183.09	$183.10	$183.10
Purchase #5	$10.44	8.355%	$11.3123	$11.31	$11.30	$11.30
Purchase #6	$59.68	7.847%	$64.3631	$64.36	$64.35	$64.40
Purchase #7	$218.90	4.849%	$229.5145	$229.51	$229.50	$229.50
7 purchase totals =	$705.76		$758.7505	$758.75	$758.70	$758.80