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	$209.57	11.435%	$233.5343	$233.53	$233.55	$233.50
Purchase #2	$137.35	13.380%	$155.7274	$155.73	$155.75	$155.70
Purchase #3	$18.45	10.432%	$20.3747	$20.37	$20.35	$20.40
Purchase #4	$186.81	12.752%	$210.632	$210.63	$210.65	$210.60
Purchase #5	$200.81	11.435%	$223.7726	$223.77	$223.75	$223.80
Purchase #6	$137.94	12.318%	$154.9314	$154.93	$154.95	$154.90
Purchase #7	$77.80	10.271%	$85.7908	$85.79	$85.80	$85.80
7 purchase totals =	$968.73		$1,084.7632	$1,084.75	$1,084.80	$1,084.70