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	$135.62	7.565%	$145.8797	$145.88	$145.90	$145.90
Purchase #2	$76.29	12.612%	$85.9117	$85.91	$85.90	$85.90
Purchase #3	$140.69	8.111%	$152.1014	$152.10	$152.10	$152.10
Purchase #4	$152.77	7.614%	$164.4019	$164.40	$164.40	$164.40
Purchase #5	$135.83	6.825%	$145.1004	$145.10	$145.10	$145.10
Purchase #6	$33.35	7.683%	$35.9123	$35.91	$35.90	$35.90
Purchase #7	$218.82	5.488%	$230.8288	$230.83	$230.85	$230.80
7 purchase totals =	$893.37		$960.1362	$960.13	$960.15	$960.10