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	$162.63	5.477%	$171.5372	$171.54	$171.55	$171.50
Purchase #2	$119.46	9.228%	$130.4838	$130.48	$130.50	$130.50
Purchase #3	$77.27	6.158%	$82.0283	$82.03	$82.05	$82.00
Purchase #4	$129.63	9.579%	$142.0473	$142.05	$142.05	$142.00
Purchase #5	$60.49	11.862%	$67.6653	$67.67	$67.65	$67.70
Purchase #6	$77.27	8.532%	$83.8627	$83.86	$83.85	$83.90
Purchase #7	$143.68	4.488%	$150.1284	$150.13	$150.15	$150.10
7 purchase totals =	$770.43		$827.7530	$827.76	$827.80	$827.70