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	$98.74	13.266%	$111.8388	$111.84	$111.85	$111.80
Purchase #2	$247.61	3.746%	$256.8855	$256.89	$256.90	$256.90
Purchase #3	$44.38	12.787%	$50.0549	$50.05	$50.05	$50.10
Purchase #4	$136.97	8.658%	$148.8289	$148.83	$148.85	$148.80
Purchase #5	$95.92	8.236%	$103.82	$103.82	$103.80	$103.80
Purchase #6	$97.67	12.280%	$109.6639	$109.66	$109.65	$109.70
Purchase #7	$43.29	8.615%	$47.0194	$47.02	$47.00	$47.00
7 purchase totals =	$764.58		$828.1114	$828.11	$828.10	$828.10