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	$57.99	7.832%	$62.5318	$62.53	$62.55	$62.50
Purchase #2	$143.48	7.843%	$154.7331	$154.73	$154.75	$154.70
Purchase #3	$70.95	10.722%	$78.5573	$78.56	$78.55	$78.60
Purchase #4	$83.96	7.328%	$90.1126	$90.11	$90.10	$90.10
Purchase #5	$190.36	12.718%	$214.57	$214.57	$214.55	$214.60
Purchase #6	$31.92	12.196%	$35.813	$35.81	$35.80	$35.80
Purchase #7	$186.43	4.362%	$194.5621	$194.56	$194.55	$194.60
7 purchase totals =	$765.09		$830.8799	$830.87	$830.85	$830.90