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	$70.49	3.158%	$72.7161	$72.72	$72.70	$72.70
Purchase #2	$121.28	5.838%	$128.3603	$128.36	$128.35	$128.40
Purchase #3	$11.76	8.573%	$12.7682	$12.77	$12.75	$12.80
Purchase #4	$63.94	10.668%	$70.7611	$70.76	$70.75	$70.80
Purchase #5	$127.83	3.123%	$131.8221	$131.82	$131.80	$131.80
Purchase #6	$100.65	8.277%	$108.9808	$108.98	$109.00	$109.00
Purchase #7	$189.75	11.266%	$211.1272	$211.13	$211.15	$211.10
7 purchase totals =	$685.70		$736.5358	$736.54	$736.50	$736.60