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	$156.83	7.506%	$168.6017	$168.60	$168.60	$168.60
Purchase #2	$210.28	11.431%	$234.3171	$234.32	$234.30	$234.30
Purchase #3	$104.51	3.205%	$107.8595	$107.86	$107.85	$107.90
Purchase #4	$112.62	5.420%	$118.724	$118.72	$118.70	$118.70
Purchase #5	$55.99	9.640%	$61.3874	$61.39	$61.40	$61.40
Purchase #6	$194.40	8.794%	$211.4955	$211.50	$211.50	$211.50
Purchase #7	$145.40	9.378%	$159.0356	$159.04	$159.05	$159.00
7 purchase totals =	$980.03		$1,061.4208	$1,061.43	$1,061.40	$1,061.40