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	$57.60	9.820%	$63.2563	$63.26	$63.25	$63.30
Purchase #2	$104.46	9.507%	$114.391	$114.39	$114.40	$114.40
Purchase #3	$140.35	13.619%	$159.4643	$159.46	$159.45	$159.50
Purchase #4	$57.41	8.556%	$62.322	$62.32	$62.30	$62.30
Purchase #5	$185.29	5.148%	$194.8287	$194.83	$194.85	$194.80
Purchase #6	$19.29	6.546%	$20.5527	$20.55	$20.55	$20.60
Purchase #7	$201.51	10.450%	$222.5678	$222.57	$222.55	$222.60
7 purchase totals =	$765.91		$837.3828	$837.38	$837.35	$837.50