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	$92.90	10.153%	$102.3321	$102.33	$102.35	$102.30
Purchase #2	$239.95	4.214%	$250.0615	$250.06	$250.05	$250.10
Purchase #3	$115.73	10.446%	$127.8192	$127.82	$127.80	$127.80
Purchase #4	$151.84	6.841%	$162.2274	$162.23	$162.25	$162.20
Purchase #5	$203.82	3.667%	$211.2941	$211.29	$211.30	$211.30
Purchase #6	$76.85	5.377%	$80.9822	$80.98	$81.00	$81.00
Purchase #7	$205.34	4.330%	$214.2312	$214.23	$214.25	$214.20
7 purchase totals =	$1,086.43		$1,148.9477	$1,148.94	$1,149.00	$1,148.90