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	$215.82	6.289%	$229.3929	$229.39	$229.40	$229.40
Purchase #2	$249.51	13.692%	$283.6729	$283.67	$283.65	$283.70
Purchase #3	$110.75	3.712%	$114.861	$114.86	$114.85	$114.90
Purchase #4	$10.61	6.274%	$11.2757	$11.28	$11.30	$11.30
Purchase #5	$17.71	4.369%	$18.4837	$18.48	$18.50	$18.50
Purchase #6	$47.71	11.171%	$53.0397	$53.04	$53.05	$53.00
Purchase #7	$59.70	4.404%	$62.3292	$62.33	$62.35	$62.30
7 purchase totals =	$711.81		$773.0551	$773.05	$773.10	$773.10