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	$127.92	9.340%	$139.8677	$139.87	$139.85	$139.90
Purchase #2	$158.98	13.653%	$180.6855	$180.69	$180.70	$180.70
Purchase #3	$153.74	5.106%	$161.59	$161.59	$161.60	$161.60
Purchase #4	$168.84	3.681%	$175.055	$175.06	$175.05	$175.10
Purchase #5	$89.60	7.539%	$96.3549	$96.35	$96.35	$96.40
Purchase #6	$140.51	11.139%	$156.1614	$156.16	$156.15	$156.20
Purchase #7	$164.81	5.171%	$173.3323	$173.33	$173.35	$173.30
7 purchase totals =	$1,004.40		$1,083.0468	$1,083.05	$1,083.05	$1,083.20