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	$150.95	11.739%	$168.67	$168.67	$168.65	$168.70
Purchase #2	$50.26	11.194%	$55.8861	$55.89	$55.90	$55.90
Purchase #3	$167.78	12.423%	$188.6233	$188.62	$188.60	$188.60
Purchase #4	$89.62	3.167%	$92.4583	$92.46	$92.45	$92.50
Purchase #5	$99.27	9.611%	$108.8108	$108.81	$108.80	$108.80
Purchase #6	$233.88	6.131%	$248.2192	$248.22	$248.20	$248.20
Purchase #7	$249.70	13.270%	$282.8352	$282.84	$282.85	$282.80
7 purchase totals =	$1,041.46		$1,145.5029	$1,145.51	$1,145.45	$1,145.50