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	$207.53	7.859%	$223.8398	$223.84	$223.85	$223.80
Purchase #2	$142.47	4.470%	$148.8384	$148.84	$148.85	$148.80
Purchase #3	$216.36	5.174%	$227.5545	$227.55	$227.55	$227.60
Purchase #4	$168.89	7.163%	$180.9876	$180.99	$181.00	$181.00
Purchase #5	$53.89	10.771%	$59.6945	$59.69	$59.70	$59.70
Purchase #6	$249.77	11.615%	$278.7808	$278.78	$278.80	$278.80
Purchase #7	$86.29	5.654%	$91.1688	$91.17	$91.15	$91.20
7 purchase totals =	$1,125.20		$1,210.8644	$1,210.86	$1,210.90	$1,210.90