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	$172.35	8.647%	$187.2531	$187.25	$187.25	$187.30
Purchase #2	$105.44	4.582%	$110.2713	$110.27	$110.25	$110.30
Purchase #3	$234.89	11.748%	$262.4849	$262.48	$262.50	$262.50
Purchase #4	$170.50	11.279%	$189.7307	$189.73	$189.75	$189.70
Purchase #5	$178.46	10.128%	$196.5344	$196.53	$196.55	$196.50
Purchase #6	$211.47	4.220%	$220.394	$220.39	$220.40	$220.40
Purchase #7	$45.94	11.365%	$51.1611	$51.16	$51.15	$51.20
7 purchase totals =	$1,119.05		$1,217.8295	$1,217.81	$1,217.85	$1,217.90