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	$99.25	5.296%	$104.5063	$104.51	$104.50	$104.50
Purchase #2	$166.90	9.280%	$182.3883	$182.39	$182.40	$182.40
Purchase #3	$187.73	10.248%	$206.9686	$206.97	$206.95	$207.00
Purchase #4	$144.91	8.675%	$157.4809	$157.48	$157.50	$157.50
Purchase #5	$100.47	10.276%	$110.7943	$110.79	$110.80	$110.80
Purchase #6	$57.95	5.497%	$61.1355	$61.14	$61.15	$61.10
Purchase #7	$171.88	4.329%	$179.3207	$179.32	$179.30	$179.30
7 purchase totals =	$929.09		$1,002.5946	$1,002.60	$1,002.60	$1,002.60