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	$96.36	13.144%	$109.0256	$109.03	$109.05	$109.00
Purchase #2	$7.58	9.159%	$8.2743	$8.27	$8.25	$8.30
Purchase #3	$5.70	7.835%	$6.1466	$6.15	$6.15	$6.10
Purchase #4	$18.79	10.461%	$20.7556	$20.76	$20.75	$20.80
Purchase #5	$169.55	8.674%	$184.2568	$184.26	$184.25	$184.30
Purchase #6	$52.39	13.786%	$59.6125	$59.61	$59.60	$59.60
Purchase #7	$215.88	10.634%	$238.8367	$238.84	$238.85	$238.80
7 purchase totals =	$566.25		$626.9081	$626.92	$626.90	$626.90