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	$48.82	11.236%	$54.3054	$54.31	$54.30	$54.30
Purchase #2	$87.96	5.235%	$92.5647	$92.56	$92.55	$92.60
Purchase #3	$86.43	11.514%	$96.3816	$96.38	$96.40	$96.40
Purchase #4	$142.32	11.272%	$158.3623	$158.36	$158.35	$158.40
Purchase #5	$181.92	9.714%	$199.5917	$199.59	$199.60	$199.60
Purchase #6	$212.89	8.618%	$231.2369	$231.24	$231.25	$231.20
Purchase #7	$215.98	11.647%	$241.1352	$241.14	$241.15	$241.10
7 purchase totals =	$976.32		$1,073.5778	$1,073.58	$1,073.60	$1,073.60