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	$40.88	8.758%	$44.4603	$44.46	$44.45	$44.50
Purchase #2	$25.29	11.289%	$28.145	$28.15	$28.15	$28.10
Purchase #3	$31.58	10.436%	$34.8757	$34.88	$34.90	$34.90
Purchase #4	$88.74	11.119%	$98.607	$98.61	$98.60	$98.60
Purchase #5	$73.60	11.501%	$82.0647	$82.06	$82.05	$82.10
Purchase #6	$107.42	9.475%	$117.598	$117.60	$117.60	$117.60
Purchase #7	$174.59	11.732%	$195.0729	$195.07	$195.05	$195.10
7 purchase totals =	$542.10		$600.8236	$600.83	$600.80	$600.90