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	$72.69	8.313%	$78.7327	$78.73	$78.75	$78.70
Purchase #2	$202.78	10.217%	$223.498	$223.50	$223.50	$223.50
Purchase #3	$69.55	11.616%	$77.6289	$77.63	$77.65	$77.60
Purchase #4	$177.32	10.751%	$196.3837	$196.38	$196.40	$196.40
Purchase #5	$115.78	5.643%	$122.3135	$122.31	$122.30	$122.30
Purchase #6	$142.77	9.867%	$156.8571	$156.86	$156.85	$156.90
Purchase #7	$159.56	5.369%	$168.1268	$168.13	$168.15	$168.10
7 purchase totals =	$940.45		$1,023.5407	$1,023.54	$1,023.60	$1,023.50