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	$104.74	4.489%	$109.4418	$109.44	$109.45	$109.40
Purchase #2	$92.91	8.483%	$100.7916	$100.79	$100.80	$100.80
Purchase #3	$26.41	7.549%	$28.4037	$28.40	$28.40	$28.40
Purchase #4	$138.44	13.495%	$157.1225	$157.12	$157.10	$157.10
Purchase #5	$106.75	11.396%	$118.9152	$118.92	$118.90	$118.90
Purchase #6	$178.52	12.288%	$200.4565	$200.46	$200.45	$200.50
Purchase #7	$136.79	11.749%	$152.8615	$152.86	$152.85	$152.90
7 purchase totals =	$784.56		$867.9928	$867.99	$867.95	$868.00