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	$52.53	5.115%	$55.2169	$55.22	$55.20	$55.20
Purchase #2	$7.47	6.137%	$7.9284	$7.93	$7.95	$7.90
Purchase #3	$190.61	6.818%	$203.6058	$203.61	$203.60	$203.60
Purchase #4	$78.93	4.579%	$82.5442	$82.54	$82.55	$82.50
Purchase #5	$208.71	11.825%	$233.39	$233.39	$233.40	$233.40
Purchase #6	$98.64	13.367%	$111.8252	$111.83	$111.85	$111.80
Purchase #7	$92.53	3.783%	$96.0304	$96.03	$96.05	$96.00
7 purchase totals =	$729.42		$790.5409	$790.55	$790.60	$790.40