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	$104.64	5.303%	$110.1891	$110.19	$110.20	$110.20
Purchase #2	$245.34	8.780%	$266.8809	$266.88	$266.90	$266.90
Purchase #3	$67.49	7.680%	$72.6732	$72.67	$72.65	$72.70
Purchase #4	$92.34	13.261%	$104.5852	$104.59	$104.60	$104.60
Purchase #5	$115.49	6.802%	$123.3456	$123.35	$123.35	$123.30
Purchase #6	$55.44	7.306%	$59.4904	$59.49	$59.50	$59.50
Purchase #7	$120.36	9.190%	$131.4211	$131.42	$131.40	$131.40
7 purchase totals =	$801.10		$868.5855	$868.59	$868.60	$868.60