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	$227.75	13.781%	$259.1362	$259.14	$259.15	$259.10
Purchase #2	$64.38	5.453%	$67.8906	$67.89	$67.90	$67.90
Purchase #3	$5.90	7.243%	$6.3273	$6.33	$6.35	$6.30
Purchase #4	$130.83	7.152%	$140.187	$140.19	$140.20	$140.20
Purchase #5	$17.61	8.635%	$19.1306	$19.13	$19.15	$19.10
Purchase #6	$12.26	8.210%	$13.2665	$13.27	$13.25	$13.30
Purchase #7	$152.76	5.796%	$161.614	$161.61	$161.60	$161.60
7 purchase totals =	$611.49		$667.5522	$667.56	$667.60	$667.50