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	$249.50	12.782%	$281.3911	$281.39	$281.40	$281.40
Purchase #2	$194.84	10.356%	$215.0176	$215.02	$215.00	$215.00
Purchase #3	$133.50	4.554%	$139.5796	$139.58	$139.60	$139.60
Purchase #4	$41.49	5.431%	$43.7433	$43.74	$43.75	$43.70
Purchase #5	$19.41	5.787%	$20.5333	$20.53	$20.55	$20.50
Purchase #6	$158.38	9.426%	$173.3089	$173.31	$173.30	$173.30
Purchase #7	$151.76	4.594%	$158.7319	$158.73	$158.75	$158.70
7 purchase totals =	$948.88		$1,032.3057	$1,032.30	$1,032.35	$1,032.20