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	$67.41	9.430%	$73.7668	$73.77	$73.75	$73.80
Purchase #2	$156.86	12.544%	$176.5365	$176.54	$176.55	$176.50
Purchase #3	$64.58	12.113%	$72.4026	$72.40	$72.40	$72.40
Purchase #4	$197.97	8.200%	$214.2035	$214.20	$214.20	$214.20
Purchase #5	$33.31	7.470%	$35.7983	$35.80	$35.80	$35.80
Purchase #6	$175.27	12.277%	$196.7879	$196.79	$196.80	$196.80
Purchase #7	$166.66	3.383%	$172.2981	$172.30	$172.30	$172.30
7 purchase totals =	$862.06		$941.7937	$941.80	$941.80	$941.80