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	$184.71	8.555%	$200.5119	$200.51	$200.50	$200.50
Purchase #2	$90.62	9.845%	$99.5415	$99.54	$99.55	$99.50
Purchase #3	$157.32	13.346%	$178.3159	$178.32	$178.30	$178.30
Purchase #4	$12.57	6.327%	$13.3653	$13.37	$13.35	$13.40
Purchase #5	$66.97	7.112%	$71.7329	$71.73	$71.75	$71.70
Purchase #6	$177.61	10.597%	$196.4313	$196.43	$196.45	$196.40
Purchase #7	$167.53	10.104%	$184.4572	$184.46	$184.45	$184.50
7 purchase totals =	$857.33		$944.3560	$944.36	$944.35	$944.30