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	$74.39	11.752%	$83.1323	$83.13	$83.15	$83.10
Purchase #2	$79.75	7.487%	$85.7209	$85.72	$85.70	$85.70
Purchase #3	$164.72	5.172%	$173.2393	$173.24	$173.25	$173.20
Purchase #4	$122.82	3.494%	$127.1113	$127.11	$127.10	$127.10
Purchase #5	$210.85	12.630%	$237.4804	$237.48	$237.50	$237.50
Purchase #6	$241.67	11.260%	$268.882	$268.88	$268.90	$268.90
Purchase #7	$207.38	10.628%	$229.4203	$229.42	$229.40	$229.40
7 purchase totals =	$1,101.58		$1,204.9865	$1,204.98	$1,205.00	$1,204.90