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	$211.40	12.593%	$238.0216	$238.02	$238.00	$238.00
Purchase #2	$60.65	3.790%	$62.9486	$62.95	$62.95	$62.90
Purchase #3	$6.84	12.754%	$7.7124	$7.71	$7.70	$7.70
Purchase #4	$48.84	12.751%	$55.0676	$55.07	$55.05	$55.10
Purchase #5	$82.97	7.732%	$89.3852	$89.39	$89.40	$89.40
Purchase #6	$221.78	13.129%	$250.8975	$250.90	$250.90	$250.90
Purchase #7	$158.43	11.616%	$176.8332	$176.83	$176.85	$176.80
7 purchase totals =	$790.91		$880.8661	$880.87	$880.85	$880.80