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	$85.73	12.359%	$96.3254	$96.33	$96.35	$96.30
Purchase #2	$41.38	13.225%	$46.8525	$46.85	$46.85	$46.90
Purchase #3	$222.30	12.219%	$249.4628	$249.46	$249.45	$249.50
Purchase #4	$175.31	6.775%	$187.1873	$187.19	$187.20	$187.20
Purchase #5	$50.33	8.806%	$54.7621	$54.76	$54.75	$54.80
Purchase #6	$238.29	5.359%	$251.06	$251.06	$251.05	$251.10
Purchase #7	$126.35	3.462%	$130.7242	$130.72	$130.70	$130.70
7 purchase totals =	$939.69		$1,016.3743	$1,016.37	$1,016.35	$1,016.50