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	$197.60	11.282%	$219.8932	$219.89	$219.90	$219.90
Purchase #2	$114.52	4.727%	$119.9334	$119.93	$119.95	$119.90
Purchase #3	$94.86	4.702%	$99.3203	$99.32	$99.30	$99.30
Purchase #4	$106.41	4.803%	$111.5209	$111.52	$111.50	$111.50
Purchase #5	$234.32	3.755%	$243.1187	$243.12	$243.10	$243.10
Purchase #6	$83.43	6.772%	$89.0799	$89.08	$89.10	$89.10
Purchase #7	$107.75	4.410%	$112.5018	$112.50	$112.50	$112.50
7 purchase totals =	$938.89		$995.3682	$995.36	$995.35	$995.30