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	$218.56	7.476%	$234.8995	$234.90	$234.90	$234.90
Purchase #2	$39.32	3.641%	$40.7516	$40.75	$40.75	$40.80
Purchase #3	$91.34	10.729%	$101.1399	$101.14	$101.15	$101.10
Purchase #4	$113.40	12.526%	$127.6045	$127.60	$127.60	$127.60
Purchase #5	$194.95	5.527%	$205.7249	$205.72	$205.70	$205.70
Purchase #6	$92.84	4.383%	$96.9092	$96.91	$96.90	$96.90
Purchase #7	$49.56	6.146%	$52.606	$52.61	$52.60	$52.60
7 purchase totals =	$799.97		$859.6356	$859.63	$859.60	$859.60