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	$127.64	3.786%	$132.4725	$132.47	$132.45	$132.50
Purchase #2	$83.38	8.416%	$90.3973	$90.40	$90.40	$90.40
Purchase #3	$162.39	12.591%	$182.8365	$182.84	$182.85	$182.80
Purchase #4	$239.92	12.290%	$269.4062	$269.41	$269.40	$269.40
Purchase #5	$233.92	3.414%	$241.906	$241.91	$241.90	$241.90
Purchase #6	$96.36	11.656%	$107.5917	$107.59	$107.60	$107.60
Purchase #7	$130.72	3.863%	$135.7697	$135.77	$135.75	$135.80
7 purchase totals =	$1,074.33		$1,160.3799	$1,160.39	$1,160.35	$1,160.40