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	$55.25	8.279%	$59.8241	$59.82	$59.80	$59.80
Purchase #2	$151.83	4.728%	$159.0085	$159.01	$159.00	$159.00
Purchase #3	$62.84	7.482%	$67.5417	$67.54	$67.55	$67.50
Purchase #4	$107.74	8.481%	$116.8774	$116.88	$116.90	$116.90
Purchase #5	$65.70	10.257%	$72.4388	$72.44	$72.45	$72.40
Purchase #6	$159.27	6.585%	$169.7579	$169.76	$169.75	$169.80
Purchase #7	$192.75	8.866%	$209.8392	$209.84	$209.85	$209.80
7 purchase totals =	$795.38		$855.2876	$855.29	$855.30	$855.20