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	$105.81	8.202%	$114.4885	$114.49	$114.50	$114.50
Purchase #2	$130.57	12.473%	$146.856	$146.86	$146.85	$146.90
Purchase #3	$219.27	6.772%	$234.119	$234.12	$234.10	$234.10
Purchase #4	$38.96	10.730%	$43.1404	$43.14	$43.15	$43.10
Purchase #5	$56.43	3.124%	$58.1929	$58.19	$58.20	$58.20
Purchase #6	$160.32	3.682%	$166.223	$166.22	$166.20	$166.20
Purchase #7	$229.97	3.442%	$237.8856	$237.89	$237.90	$237.90
7 purchase totals =	$941.33		$1,000.9054	$1,000.91	$1,000.90	$1,000.90