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	$202.81	10.175%	$223.4459	$223.45	$223.45	$223.40
Purchase #2	$214.38	11.233%	$238.4613	$238.46	$238.45	$238.50
Purchase #3	$155.92	5.499%	$164.494	$164.49	$164.50	$164.50
Purchase #4	$84.62	7.400%	$90.8819	$90.88	$90.90	$90.90
Purchase #5	$118.28	9.377%	$129.3711	$129.37	$129.35	$129.40
Purchase #6	$93.26	5.142%	$98.0554	$98.06	$98.05	$98.10
Purchase #7	$190.77	11.682%	$213.0558	$213.06	$213.05	$213.10
7 purchase totals =	$1,060.04		$1,157.7654	$1,157.77	$1,157.75	$1,157.90