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	$85.60	4.489%	$89.4426	$89.44	$89.45	$89.40
Purchase #2	$112.97	6.741%	$120.5853	$120.59	$120.60	$120.60
Purchase #3	$42.75	6.535%	$45.5437	$45.54	$45.55	$45.50
Purchase #4	$98.61	9.715%	$108.19	$108.19	$108.20	$108.20
Purchase #5	$71.56	3.476%	$74.0474	$74.05	$74.05	$74.00
Purchase #6	$78.29	4.220%	$81.5938	$81.59	$81.60	$81.60
Purchase #7	$62.44	8.524%	$67.7624	$67.76	$67.75	$67.80
7 purchase totals =	$552.22		$587.1652	$587.16	$587.20	$587.10