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	$68.91	5.862%	$72.9495	$72.95	$72.95	$72.90
Purchase #2	$152.91	8.348%	$165.6749	$165.67	$165.65	$165.70
Purchase #3	$79.99	10.303%	$88.2314	$88.23	$88.25	$88.20
Purchase #4	$48.46	6.130%	$51.4306	$51.43	$51.45	$51.40
Purchase #5	$211.53	3.484%	$218.8997	$218.90	$218.90	$218.90
Purchase #6	$239.65	12.860%	$270.469	$270.47	$270.45	$270.50
Purchase #7	$73.38	12.582%	$82.6127	$82.61	$82.60	$82.60
7 purchase totals =	$874.83		$950.2678	$950.26	$950.25	$950.20