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	$51.33	6.750%	$54.7948	$54.79	$54.80	$54.80
Purchase #2	$168.81	6.163%	$179.2138	$179.21	$179.20	$179.20
Purchase #3	$69.62	3.868%	$72.3129	$72.31	$72.30	$72.30
Purchase #4	$210.69	11.337%	$234.5759	$234.58	$234.60	$234.60
Purchase #5	$216.61	4.865%	$227.1481	$227.15	$227.15	$227.10
Purchase #6	$86.29	3.217%	$89.0659	$89.07	$89.05	$89.10
Purchase #7	$179.27	7.302%	$192.3603	$192.36	$192.35	$192.40
7 purchase totals =	$982.62		$1,049.4717	$1,049.47	$1,049.45	$1,049.50