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	$134.50	6.693%	$143.5021	$143.50	$143.50	$143.50
Purchase #2	$102.70	5.700%	$108.5539	$108.55	$108.55	$108.60
Purchase #3	$110.47	5.474%	$116.5171	$116.52	$116.50	$116.50
Purchase #4	$114.99	11.669%	$128.4082	$128.41	$128.40	$128.40
Purchase #5	$239.72	4.540%	$250.6033	$250.60	$250.60	$250.60
Purchase #6	$160.64	6.385%	$170.8969	$170.90	$170.90	$170.90
Purchase #7	$84.76	7.791%	$91.3637	$91.36	$91.35	$91.40
7 purchase totals =	$947.78		$1,009.8452	$1,009.84	$1,009.80	$1,009.90