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	$168.97	8.205%	$182.834	$182.83	$182.85	$182.80
Purchase #2	$71.50	3.321%	$73.8745	$73.87	$73.85	$73.90
Purchase #3	$155.55	11.561%	$173.5331	$173.53	$173.55	$173.50
Purchase #4	$216.65	6.305%	$230.3098	$230.31	$230.30	$230.30
Purchase #5	$57.57	12.496%	$64.7639	$64.76	$64.75	$64.80
Purchase #6	$27.75	13.123%	$31.3916	$31.39	$31.40	$31.40
Purchase #7	$60.38	11.572%	$67.3672	$67.37	$67.35	$67.40
7 purchase totals =	$758.37		$824.0741	$824.06	$824.05	$824.10