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	$191.66	10.285%	$211.3722	$211.37	$211.35	$211.40
Purchase #2	$40.66	3.399%	$42.042	$42.04	$42.05	$42.00
Purchase #3	$59.30	6.407%	$63.0994	$63.10	$63.10	$63.10
Purchase #4	$149.71	6.770%	$159.8454	$159.85	$159.85	$159.80
Purchase #5	$188.30	11.276%	$209.5327	$209.53	$209.55	$209.50
Purchase #6	$124.86	11.693%	$139.4599	$139.46	$139.45	$139.50
Purchase #7	$136.45	13.327%	$154.6347	$154.63	$154.65	$154.60
7 purchase totals =	$890.94		$979.9863	$979.98	$980.00	$979.90