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	$51.32	9.239%	$56.0615	$56.06	$56.05	$56.10
Purchase #2	$85.62	4.775%	$89.7084	$89.71	$89.70	$89.70
Purchase #3	$21.50	13.711%	$24.4479	$24.45	$24.45	$24.40
Purchase #4	$116.78	5.744%	$123.4878	$123.49	$123.50	$123.50
Purchase #5	$57.48	4.223%	$59.9074	$59.91	$59.90	$59.90
Purchase #6	$77.53	7.120%	$83.0501	$83.05	$83.05	$83.10
Purchase #7	$35.59	10.667%	$39.3864	$39.39	$39.40	$39.40
7 purchase totals =	$445.82		$476.0495	$476.06	$476.05	$476.10