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	$66.26	6.830%	$70.7856	$70.79	$70.80	$70.80
Purchase #2	$79.64	3.406%	$82.3525	$82.35	$82.35	$82.40
Purchase #3	$65.61	12.419%	$73.7581	$73.76	$73.75	$73.80
Purchase #4	$185.30	6.285%	$196.9461	$196.95	$196.95	$196.90
Purchase #5	$103.91	8.221%	$112.4524	$112.45	$112.45	$112.50
Purchase #6	$81.90	5.278%	$86.2227	$86.22	$86.20	$86.20
Purchase #7	$96.50	11.175%	$107.2839	$107.28	$107.30	$107.30
7 purchase totals =	$679.12		$729.8013	$729.80	$729.80	$729.90