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	$91.67	5.481%	$96.6944	$96.69	$96.70	$96.70
Purchase #2	$232.44	10.248%	$256.2605	$256.26	$256.25	$256.30
Purchase #3	$48.32	8.732%	$52.5393	$52.54	$52.55	$52.50
Purchase #4	$101.50	11.432%	$113.1035	$113.10	$113.10	$113.10
Purchase #5	$101.53	9.618%	$111.2952	$111.30	$111.30	$111.30
Purchase #6	$119.96	9.516%	$131.3754	$131.38	$131.40	$131.40
Purchase #7	$94.92	5.188%	$99.8444	$99.84	$99.85	$99.80
7 purchase totals =	$790.34		$861.1127	$861.11	$861.15	$861.10