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	$171.41	13.280%	$194.1732	$194.17	$194.15	$194.20
Purchase #2	$91.73	7.443%	$98.5575	$98.56	$98.55	$98.60
Purchase #3	$59.35	13.692%	$67.4762	$67.48	$67.50	$67.50
Purchase #4	$33.97	8.285%	$36.7844	$36.78	$36.80	$36.80
Purchase #5	$53.69	12.463%	$60.3814	$60.38	$60.40	$60.40
Purchase #6	$157.82	13.843%	$179.667	$179.67	$179.65	$179.70
Purchase #7	$129.56	9.426%	$141.7723	$141.77	$141.75	$141.80
7 purchase totals =	$697.53		$778.8120	$778.81	$778.80	$779.00