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	$191.84	4.585%	$200.6359	$200.64	$200.65	$200.60
Purchase #2	$249.38	3.267%	$257.5272	$257.53	$257.55	$257.50
Purchase #3	$78.54	9.683%	$86.145	$86.15	$86.15	$86.10
Purchase #4	$25.35	10.217%	$27.94	$27.94	$27.95	$27.90
Purchase #5	$53.78	10.365%	$59.3543	$59.35	$59.35	$59.40
Purchase #6	$104.76	6.110%	$111.1608	$111.16	$111.15	$111.20
Purchase #7	$225.44	8.772%	$245.2156	$245.22	$245.20	$245.20
7 purchase totals =	$929.09		$987.9788	$987.99	$988.00	$987.90