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	$157.80	4.751%	$165.2971	$165.30	$165.30	$165.30
Purchase #2	$145.37	7.532%	$156.3193	$156.32	$156.30	$156.30
Purchase #3	$14.25	4.418%	$14.8796	$14.88	$14.90	$14.90
Purchase #4	$55.53	8.587%	$60.2984	$60.30	$60.30	$60.30
Purchase #5	$204.70	7.172%	$219.3811	$219.38	$219.40	$219.40
Purchase #6	$142.43	7.124%	$152.5767	$152.58	$152.60	$152.60
Purchase #7	$196.55	4.753%	$205.892	$205.89	$205.90	$205.90
7 purchase totals =	$916.63		$974.6442	$974.65	$974.70	$974.70