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	$159.49	8.445%	$172.9589	$172.96	$172.95	$173.00
Purchase #2	$110.79	13.607%	$125.8652	$125.87	$125.85	$125.90
Purchase #3	$67.93	6.491%	$72.3393	$72.34	$72.35	$72.30
Purchase #4	$60.76	11.552%	$67.779	$67.78	$67.80	$67.80
Purchase #5	$82.26	9.503%	$90.0772	$90.08	$90.10	$90.10
Purchase #6	$199.44	8.287%	$215.9676	$215.97	$215.95	$216.00
Purchase #7	$241.49	9.413%	$264.2215	$264.22	$264.20	$264.20
7 purchase totals =	$922.16		$1,009.2087	$1,009.22	$1,009.20	$1,009.30