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	$42.28	8.868%	$46.0294	$46.03	$46.05	$46.00
Purchase #2	$125.78	13.724%	$143.042	$143.04	$143.05	$143.00
Purchase #3	$17.36	6.247%	$18.4445	$18.44	$18.45	$18.40
Purchase #4	$238.54	5.120%	$250.7532	$250.75	$250.75	$250.80
Purchase #5	$19.50	5.767%	$20.6246	$20.62	$20.60	$20.60
Purchase #6	$68.93	4.865%	$72.2834	$72.28	$72.30	$72.30
Purchase #7	$180.86	9.787%	$198.5608	$198.56	$198.55	$198.60
7 purchase totals =	$693.25		$749.7379	$749.72	$749.75	$749.70