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	$76.84	5.316%	$80.9248	$80.92	$80.90	$80.90
Purchase #2	$108.33	11.621%	$120.919	$120.92	$120.90	$120.90
Purchase #3	$189.34	5.804%	$200.3293	$200.33	$200.35	$200.30
Purchase #4	$100.59	3.139%	$103.7475	$103.75	$103.75	$103.70
Purchase #5	$143.26	9.436%	$156.778	$156.78	$156.80	$156.80
Purchase #6	$205.98	10.820%	$228.267	$228.27	$228.25	$228.30
Purchase #7	$197.48	6.769%	$210.8474	$210.85	$210.85	$210.80
7 purchase totals =	$1,021.82		$1,101.8130	$1,101.82	$1,101.80	$1,101.70