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	$225.25	3.440%	$232.9986	$233.00	$233.00	$233.00
Purchase #2	$152.88	4.391%	$159.593	$159.59	$159.60	$159.60
Purchase #3	$184.77	3.835%	$191.8559	$191.86	$191.85	$191.90
Purchase #4	$61.58	8.820%	$67.0114	$67.01	$67.00	$67.00
Purchase #5	$221.98	9.151%	$242.2934	$242.29	$242.30	$242.30
Purchase #6	$156.83	5.816%	$165.9512	$165.95	$165.95	$166.00
Purchase #7	$19.51	3.363%	$20.1661	$20.17	$20.15	$20.20
7 purchase totals =	$1,022.80		$1,079.8696	$1,079.87	$1,079.85	$1,080.00