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	$235.56	3.227%	$243.1615	$243.16	$243.15	$243.20
Purchase #2	$157.25	3.238%	$162.3418	$162.34	$162.35	$162.30
Purchase #3	$34.95	6.554%	$37.2406	$37.24	$37.25	$37.20
Purchase #4	$192.88	10.638%	$213.3986	$213.40	$213.40	$213.40
Purchase #5	$94.62	6.125%	$100.4155	$100.42	$100.40	$100.40
Purchase #6	$162.78	10.376%	$179.6701	$179.67	$179.65	$179.70
Purchase #7	$206.93	10.139%	$227.9106	$227.91	$227.90	$227.90
7 purchase totals =	$1,084.97		$1,164.1387	$1,164.14	$1,164.10	$1,164.10