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	$239.33	10.855%	$265.3093	$265.31	$265.30	$265.30
Purchase #2	$84.78	5.120%	$89.1207	$89.12	$89.10	$89.10
Purchase #3	$152.73	4.314%	$159.3188	$159.32	$159.30	$159.30
Purchase #4	$62.84	5.832%	$66.5048	$66.50	$66.50	$66.50
Purchase #5	$174.47	13.196%	$197.4931	$197.49	$197.50	$197.50
Purchase #6	$125.50	7.189%	$134.5222	$134.52	$134.50	$134.50
Purchase #7	$218.79	10.751%	$242.3121	$242.31	$242.30	$242.30
7 purchase totals =	$1,058.44		$1,154.5810	$1,154.57	$1,154.50	$1,154.50