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	$142.85	13.801%	$162.5647	$162.56	$162.55	$162.60
Purchase #2	$7.44	11.772%	$8.3158	$8.32	$8.30	$8.30
Purchase #3	$89.52	8.565%	$97.1874	$97.19	$97.20	$97.20
Purchase #4	$144.32	7.662%	$155.3778	$155.38	$155.40	$155.40
Purchase #5	$39.78	8.380%	$43.1136	$43.11	$43.10	$43.10
Purchase #6	$211.47	5.218%	$222.5045	$222.50	$222.50	$222.50
Purchase #7	$144.80	4.777%	$151.7171	$151.72	$151.70	$151.70
7 purchase totals =	$780.18		$840.7809	$840.78	$840.75	$840.80