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	$243.87	10.144%	$268.6082	$268.61	$268.60	$268.60
Purchase #2	$92.52	4.330%	$96.5261	$96.53	$96.55	$96.50
Purchase #3	$80.51	6.197%	$85.4992	$85.50	$85.50	$85.50
Purchase #4	$234.34	4.660%	$245.2602	$245.26	$245.25	$245.30
Purchase #5	$144.92	10.511%	$160.1525	$160.15	$160.15	$160.20
Purchase #6	$220.80	13.627%	$250.8884	$250.89	$250.90	$250.90
Purchase #7	$104.90	9.665%	$115.0386	$115.04	$115.05	$115.00
7 purchase totals =	$1,121.86		$1,221.9732	$1,221.98	$1,222.00	$1,222.00