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	$80.88	9.195%	$88.3169	$88.32	$88.30	$88.30
Purchase #2	$5.85	11.819%	$6.5414	$6.54	$6.55	$6.50
Purchase #3	$225.77	4.807%	$236.6228	$236.62	$236.60	$236.60
Purchase #4	$51.65	7.681%	$55.6172	$55.62	$55.60	$55.60
Purchase #5	$67.30	8.196%	$72.8159	$72.82	$72.80	$72.80
Purchase #6	$233.43	9.290%	$255.1156	$255.12	$255.10	$255.10
Purchase #7	$150.86	13.608%	$171.389	$171.39	$171.40	$171.40
7 purchase totals =	$815.74		$886.4188	$886.43	$886.35	$886.30