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	$191.91	4.550%	$200.6419	$200.64	$200.65	$200.60
Purchase #2	$129.59	7.330%	$139.0889	$139.09	$139.10	$139.10
Purchase #3	$188.36	11.792%	$210.5714	$210.57	$210.55	$210.60
Purchase #4	$76.95	9.759%	$84.4596	$84.46	$84.45	$84.50
Purchase #5	$131.71	13.524%	$149.5225	$149.52	$149.50	$149.50
Purchase #6	$134.45	10.675%	$148.8025	$148.80	$148.80	$148.80
Purchase #7	$79.26	13.411%	$89.8896	$89.89	$89.90	$89.90
7 purchase totals =	$932.23		$1,022.9764	$1,022.97	$1,022.95	$1,023.00