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	$33.55	7.118%	$35.9381	$35.94	$35.95	$35.90
Purchase #2	$231.56	12.539%	$260.5953	$260.60	$260.60	$260.60
Purchase #3	$69.52	3.704%	$72.095	$72.10	$72.10	$72.10
Purchase #4	$128.93	12.674%	$145.2706	$145.27	$145.25	$145.30
Purchase #5	$204.98	7.121%	$219.5766	$219.58	$219.60	$219.60
Purchase #6	$184.46	11.470%	$205.6176	$205.62	$205.60	$205.60
Purchase #7	$18.33	5.400%	$19.3198	$19.32	$19.30	$19.30
7 purchase totals =	$871.33		$958.4130	$958.43	$958.40	$958.40