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	$89.89	10.553%	$99.3761	$99.38	$99.40	$99.40
Purchase #2	$190.92	9.477%	$209.0135	$209.01	$209.00	$209.00
Purchase #3	$72.87	11.187%	$81.022	$81.02	$81.00	$81.00
Purchase #4	$69.50	12.282%	$78.036	$78.04	$78.05	$78.00
Purchase #5	$208.96	12.419%	$234.9107	$234.91	$234.90	$234.90
Purchase #6	$98.64	12.675%	$111.1426	$111.14	$111.15	$111.10
Purchase #7	$238.83	10.578%	$264.0934	$264.09	$264.10	$264.10
7 purchase totals =	$969.61		$1,077.5943	$1,077.59	$1,077.60	$1,077.50