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	$197.83	13.128%	$223.8011	$223.80	$223.80	$223.80
Purchase #2	$47.30	7.574%	$50.8825	$50.88	$50.90	$50.90
Purchase #3	$124.89	13.798%	$142.1223	$142.12	$142.10	$142.10
Purchase #4	$236.82	11.721%	$264.5777	$264.58	$264.60	$264.60
Purchase #5	$35.59	13.666%	$40.4537	$40.45	$40.45	$40.50
Purchase #6	$174.85	10.499%	$193.2075	$193.21	$193.20	$193.20
Purchase #7	$127.72	7.106%	$136.7958	$136.80	$136.80	$136.80
7 purchase totals =	$945.00		$1,051.8406	$1,051.84	$1,051.85	$1,051.90