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	$160.76	9.214%	$175.5724	$175.57	$175.55	$175.60
Purchase #2	$229.71	12.464%	$258.3411	$258.34	$258.35	$258.30
Purchase #3	$95.65	4.392%	$99.8509	$99.85	$99.85	$99.90
Purchase #4	$244.54	9.333%	$267.3629	$267.36	$267.35	$267.40
Purchase #5	$78.54	12.840%	$88.6245	$88.62	$88.60	$88.60
Purchase #6	$196.63	13.522%	$223.2183	$223.22	$223.20	$223.20
Purchase #7	$73.53	13.237%	$83.2632	$83.26	$83.25	$83.30
7 purchase totals =	$1,079.36		$1,196.2333	$1,196.22	$1,196.15	$1,196.30