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	$102.49	11.345%	$114.1175	$114.12	$114.10	$114.10
Purchase #2	$220.96	10.623%	$244.4326	$244.43	$244.45	$244.40
Purchase #3	$123.86	8.550%	$134.45	$134.45	$134.45	$134.50
Purchase #4	$125.27	9.814%	$137.564	$137.56	$137.55	$137.60
Purchase #5	$28.39	13.751%	$32.2939	$32.29	$32.30	$32.30
Purchase #6	$187.58	10.263%	$206.8313	$206.83	$206.85	$206.80
Purchase #7	$19.78	3.746%	$20.521	$20.52	$20.50	$20.50
7 purchase totals =	$808.33		$890.2103	$890.20	$890.20	$890.20