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	$67.57	6.579%	$72.0154	$72.02	$72.00	$72.00
Purchase #2	$98.58	3.685%	$102.2127	$102.21	$102.20	$102.20
Purchase #3	$106.68	4.639%	$111.6289	$111.63	$111.65	$111.60
Purchase #4	$104.75	4.269%	$109.2218	$109.22	$109.20	$109.20
Purchase #5	$219.49	11.458%	$244.6392	$244.64	$244.65	$244.60
Purchase #6	$50.35	7.626%	$54.1897	$54.19	$54.20	$54.20
Purchase #7	$92.48	7.678%	$99.5806	$99.58	$99.60	$99.60
7 purchase totals =	$739.90		$793.4883	$793.49	$793.50	$793.40