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	$27.94	5.543%	$29.4887	$29.49	$29.50	$29.50
Purchase #2	$105.58	9.478%	$115.5869	$115.59	$115.60	$115.60
Purchase #3	$78.31	6.537%	$83.4291	$83.43	$83.45	$83.40
Purchase #4	$86.54	13.809%	$98.4903	$98.49	$98.50	$98.50
Purchase #5	$183.77	6.368%	$195.4725	$195.47	$195.45	$195.50
Purchase #6	$31.90	10.674%	$35.305	$35.31	$35.30	$35.30
Purchase #7	$180.42	11.116%	$200.4755	$200.48	$200.50	$200.50
7 purchase totals =	$694.46		$758.2480	$758.26	$758.30	$758.30