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	$76.41	3.247%	$78.891	$78.89	$78.90	$78.90
Purchase #2	$89.60	3.758%	$92.9672	$92.97	$92.95	$93.00
Purchase #3	$39.92	6.107%	$42.3579	$42.36	$42.35	$42.40
Purchase #4	$9.95	8.717%	$10.8173	$10.82	$10.80	$10.80
Purchase #5	$96.34	4.459%	$100.6358	$100.64	$100.65	$100.60
Purchase #6	$80.74	6.578%	$86.0511	$86.05	$86.05	$86.10
Purchase #7	$20.59	12.605%	$23.1854	$23.19	$23.20	$23.20
7 purchase totals =	$413.55		$434.9057	$434.92	$434.90	$435.00