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	$215.54	8.783%	$234.4709	$234.47	$234.45	$234.50
Purchase #2	$95.95	5.812%	$101.5266	$101.53	$101.55	$101.50
Purchase #3	$55.90	6.860%	$59.7347	$59.73	$59.75	$59.70
Purchase #4	$144.69	5.814%	$153.1023	$153.10	$153.10	$153.10
Purchase #5	$70.59	10.669%	$78.1212	$78.12	$78.10	$78.10
Purchase #6	$70.42	12.313%	$79.0908	$79.09	$79.10	$79.10
Purchase #7	$147.82	12.520%	$166.3271	$166.33	$166.35	$166.30
7 purchase totals =	$800.91		$872.3736	$872.37	$872.40	$872.30