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	$50.87	4.817%	$53.3204	$53.32	$53.30	$53.30
Purchase #2	$73.50	3.789%	$76.2849	$76.28	$76.30	$76.30
Purchase #3	$109.49	12.594%	$123.2792	$123.28	$123.30	$123.30
Purchase #4	$119.54	6.662%	$127.5038	$127.50	$127.50	$127.50
Purchase #5	$49.74	3.685%	$51.5729	$51.57	$51.55	$51.60
Purchase #6	$171.94	12.314%	$193.1127	$193.11	$193.10	$193.10
Purchase #7	$152.36	5.310%	$160.4503	$160.45	$160.45	$160.50
7 purchase totals =	$727.44		$785.5242	$785.51	$785.50	$785.60