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	$35.81	8.280%	$38.7751	$38.78	$38.80	$38.80
Purchase #2	$130.33	8.589%	$141.524	$141.52	$141.50	$141.50
Purchase #3	$138.91	12.626%	$156.4488	$156.45	$156.45	$156.40
Purchase #4	$25.68	6.123%	$27.2524	$27.25	$27.25	$27.30
Purchase #5	$184.93	4.513%	$193.2759	$193.28	$193.30	$193.30
Purchase #6	$241.57	6.273%	$256.7237	$256.72	$256.70	$256.70
Purchase #7	$192.56	9.666%	$211.1728	$211.17	$211.15	$211.20
7 purchase totals =	$949.79		$1,025.1727	$1,025.17	$1,025.15	$1,025.20