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	$192.37	9.443%	$210.5355	$210.54	$210.55	$210.50
Purchase #2	$209.59	3.267%	$216.4373	$216.44	$216.45	$216.40
Purchase #3	$202.96	7.646%	$218.4783	$218.48	$218.50	$218.50
Purchase #4	$20.82	10.767%	$23.0617	$23.06	$23.05	$23.10
Purchase #5	$58.59	11.409%	$65.2745	$65.27	$65.25	$65.30
Purchase #6	$237.51	10.514%	$262.4818	$262.48	$262.50	$262.50
Purchase #7	$91.28	4.651%	$95.5254	$95.53	$95.55	$95.50
7 purchase totals =	$1,013.12		$1,091.7945	$1,091.80	$1,091.85	$1,091.80