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	$210.54	5.313%	$221.726	$221.73	$221.75	$221.70
Purchase #2	$18.52	12.630%	$20.8591	$20.86	$20.85	$20.90
Purchase #3	$162.29	12.612%	$182.758	$182.76	$182.75	$182.80
Purchase #4	$172.55	5.695%	$182.3767	$182.38	$182.40	$182.40
Purchase #5	$128.66	10.846%	$142.6145	$142.61	$142.60	$142.60
Purchase #6	$189.31	13.525%	$214.9142	$214.91	$214.90	$214.90
Purchase #7	$224.27	4.820%	$235.0798	$235.08	$235.10	$235.10
7 purchase totals =	$1,106.14		$1,200.3283	$1,200.33	$1,200.35	$1,200.40