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	$49.68	7.661%	$53.486	$53.49	$53.50	$53.50
Purchase #2	$95.48	8.269%	$103.3752	$103.38	$103.40	$103.40
Purchase #3	$63.30	6.117%	$67.1721	$67.17	$67.15	$67.20
Purchase #4	$245.87	9.786%	$269.9308	$269.93	$269.95	$269.90
Purchase #5	$125.71	10.307%	$138.6669	$138.67	$138.65	$138.70
Purchase #6	$178.85	5.730%	$189.0981	$189.10	$189.10	$189.10
Purchase #7	$171.60	5.211%	$180.5421	$180.54	$180.55	$180.50
7 purchase totals =	$930.49		$1,002.2712	$1,002.28	$1,002.30	$1,002.30