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	$162.60	5.726%	$171.9105	$171.91	$171.90	$171.90
Purchase #2	$99.69	5.218%	$104.8918	$104.89	$104.90	$104.90
Purchase #3	$179.79	6.112%	$190.7788	$190.78	$190.80	$190.80
Purchase #4	$73.56	10.738%	$81.4589	$81.46	$81.45	$81.50
Purchase #5	$195.56	7.696%	$210.6103	$210.61	$210.60	$210.60
Purchase #6	$233.34	4.552%	$243.9616	$243.96	$243.95	$244.00
Purchase #7	$142.45	9.692%	$156.2563	$156.26	$156.25	$156.30
7 purchase totals =	$1,086.99		$1,159.8682	$1,159.87	$1,159.85	$1,160.00