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	$90.91	7.380%	$97.6192	$97.62	$97.60	$97.60
Purchase #2	$55.35	12.318%	$62.168	$62.17	$62.15	$62.20
Purchase #3	$29.91	4.531%	$31.2652	$31.27	$31.25	$31.30
Purchase #4	$79.62	11.257%	$88.5828	$88.58	$88.60	$88.60
Purchase #5	$35.40	3.747%	$36.7264	$36.73	$36.75	$36.70
Purchase #6	$244.52	8.627%	$265.6147	$265.61	$265.60	$265.60
Purchase #7	$188.66	4.385%	$196.9327	$196.93	$196.95	$196.90
7 purchase totals =	$724.37		$778.9090	$778.91	$778.90	$778.90