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	$135.71	13.335%	$153.8069	$153.81	$153.80	$153.80
Purchase #2	$30.87	3.489%	$31.9471	$31.95	$31.95	$31.90
Purchase #3	$78.37	13.849%	$89.2235	$89.22	$89.20	$89.20
Purchase #4	$47.68	7.213%	$51.1192	$51.12	$51.10	$51.10
Purchase #5	$88.66	4.692%	$92.8199	$92.82	$92.80	$92.80
Purchase #6	$196.95	7.550%	$211.8197	$211.82	$211.80	$211.80
Purchase #7	$223.45	6.801%	$238.6468	$238.65	$238.65	$238.60
7 purchase totals =	$801.69		$869.3831	$869.39	$869.30	$869.20