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	$183.60	6.849%	$196.1748	$196.17	$196.15	$196.20
Purchase #2	$223.82	8.760%	$243.4266	$243.43	$243.45	$243.40
Purchase #3	$238.37	12.388%	$267.8993	$267.90	$267.90	$267.90
Purchase #4	$57.34	12.245%	$64.3613	$64.36	$64.35	$64.40
Purchase #5	$154.62	10.696%	$171.1582	$171.16	$171.15	$171.20
Purchase #6	$69.76	9.128%	$76.1277	$76.13	$76.15	$76.10
Purchase #7	$42.84	8.416%	$46.4454	$46.45	$46.45	$46.40
7 purchase totals =	$970.35		$1,065.5933	$1,065.60	$1,065.60	$1,065.60