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	$190.39	11.564%	$212.4067	$212.41	$212.40	$212.40
Purchase #2	$243.89	5.791%	$258.0137	$258.01	$258.00	$258.00
Purchase #3	$67.52	6.132%	$71.6603	$71.66	$71.65	$71.70
Purchase #4	$105.71	9.845%	$116.1171	$116.12	$116.10	$116.10
Purchase #5	$136.83	9.623%	$149.9972	$150.00	$150.00	$150.00
Purchase #6	$146.88	13.547%	$166.7778	$166.78	$166.80	$166.80
Purchase #7	$120.63	7.813%	$130.0548	$130.05	$130.05	$130.10
7 purchase totals =	$1,011.85		$1,105.0276	$1,105.03	$1,105.00	$1,105.10