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	$219.78	11.278%	$244.5668	$244.57	$244.55	$244.60
Purchase #2	$213.41	12.361%	$239.7896	$239.79	$239.80	$239.80
Purchase #3	$73.97	6.278%	$78.6138	$78.61	$78.60	$78.60
Purchase #4	$83.77	8.537%	$90.9214	$90.92	$90.90	$90.90
Purchase #5	$46.61	8.113%	$50.3915	$50.39	$50.40	$50.40
Purchase #6	$215.84	11.319%	$240.2709	$240.27	$240.25	$240.30
Purchase #7	$117.74	8.563%	$127.8221	$127.82	$127.80	$127.80
7 purchase totals =	$971.12		$1,072.3761	$1,072.37	$1,072.30	$1,072.40