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	$95.38	9.482%	$104.4239	$104.42	$104.40	$104.40
Purchase #2	$74.83	6.607%	$79.774	$79.77	$79.75	$79.80
Purchase #3	$81.34	11.443%	$90.6477	$90.65	$90.65	$90.60
Purchase #4	$92.37	8.198%	$99.9425	$99.94	$99.95	$99.90
Purchase #5	$191.63	4.580%	$200.4067	$200.41	$200.40	$200.40
Purchase #6	$220.49	6.523%	$234.8726	$234.87	$234.85	$234.90
Purchase #7	$224.88	7.390%	$241.4986	$241.50	$241.50	$241.50
7 purchase totals =	$980.92		$1,051.5660	$1,051.56	$1,051.50	$1,051.50