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	$222.40	7.692%	$239.507	$239.51	$239.50	$239.50
Purchase #2	$69.72	12.432%	$78.3876	$78.39	$78.40	$78.40
Purchase #3	$235.73	13.209%	$266.8676	$266.87	$266.85	$266.90
Purchase #4	$57.35	8.327%	$62.1255	$62.13	$62.15	$62.10
Purchase #5	$178.33	9.630%	$195.5032	$195.50	$195.50	$195.50
Purchase #6	$85.91	7.755%	$92.5723	$92.57	$92.55	$92.60
Purchase #7	$156.48	11.419%	$174.3485	$174.35	$174.35	$174.30
7 purchase totals =	$1,005.92		$1,109.3117	$1,109.32	$1,109.30	$1,109.30