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	$147.37	13.512%	$167.2826	$167.28	$167.30	$167.30
Purchase #2	$157.75	6.522%	$168.0385	$168.04	$168.05	$168.00
Purchase #3	$164.73	5.385%	$173.6007	$173.60	$173.60	$173.60
Purchase #4	$78.92	4.506%	$82.4761	$82.48	$82.50	$82.50
Purchase #5	$166.51	7.658%	$179.2613	$179.26	$179.25	$179.30
Purchase #6	$210.48	7.592%	$226.4596	$226.46	$226.45	$226.50
Purchase #7	$165.62	13.326%	$187.6905	$187.69	$187.70	$187.70
7 purchase totals =	$1,091.38		$1,184.8093	$1,184.81	$1,184.85	$1,184.90