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	$40.25	13.621%	$45.7325	$45.73	$45.75	$45.70
Purchase #2	$71.95	11.603%	$80.2984	$80.30	$80.30	$80.30
Purchase #3	$226.98	11.814%	$253.7954	$253.80	$253.80	$253.80
Purchase #4	$122.93	11.356%	$136.8899	$136.89	$136.90	$136.90
Purchase #5	$167.83	10.144%	$184.8547	$184.85	$184.85	$184.90
Purchase #6	$12.67	9.623%	$13.8892	$13.89	$13.90	$13.90
Purchase #7	$192.77	6.410%	$205.1266	$205.13	$205.15	$205.10
7 purchase totals =	$835.38		$920.5867	$920.59	$920.65	$920.60