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	$109.35	4.148%	$113.8858	$113.89	$113.90	$113.90
Purchase #2	$162.57	5.449%	$171.4284	$171.43	$171.45	$171.40
Purchase #3	$207.31	7.359%	$222.5659	$222.57	$222.55	$222.60
Purchase #4	$238.53	7.463%	$256.3315	$256.33	$256.35	$256.30
Purchase #5	$243.59	4.254%	$253.9523	$253.95	$253.95	$254.00
Purchase #6	$103.72	5.433%	$109.3551	$109.36	$109.35	$109.40
Purchase #7	$48.58	13.185%	$54.9853	$54.99	$55.00	$55.00
7 purchase totals =	$1,113.65		$1,182.5043	$1,182.52	$1,182.55	$1,182.60