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	$60.73	11.260%	$67.5682	$67.57	$67.55	$67.60
Purchase #2	$39.45	8.471%	$42.7918	$42.79	$42.80	$42.80
Purchase #3	$69.56	3.820%	$72.2172	$72.22	$72.20	$72.20
Purchase #4	$60.67	11.301%	$67.5263	$67.53	$67.55	$67.50
Purchase #5	$232.93	4.229%	$242.7806	$242.78	$242.80	$242.80
Purchase #6	$64.53	9.642%	$70.752	$70.75	$70.75	$70.80
Purchase #7	$46.92	8.356%	$50.8406	$50.84	$50.85	$50.80
7 purchase totals =	$574.79		$614.4767	$614.48	$614.50	$614.50