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	$172.64	9.123%	$188.3899	$188.39	$188.40	$188.40
Purchase #2	$162.98	7.103%	$174.5565	$174.56	$174.55	$174.60
Purchase #3	$43.42	12.655%	$48.9148	$48.91	$48.90	$48.90
Purchase #4	$6.70	3.823%	$6.9561	$6.96	$6.95	$7.00
Purchase #5	$160.52	6.855%	$171.5236	$171.52	$171.50	$171.50
Purchase #6	$94.35	9.572%	$103.3812	$103.38	$103.40	$103.40
Purchase #7	$123.37	3.415%	$127.5831	$127.58	$127.60	$127.60
7 purchase totals =	$763.98		$821.3052	$821.30	$821.30	$821.40