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	$193.60	9.347%	$211.6958	$211.70	$211.70	$211.70
Purchase #2	$103.51	11.451%	$115.3629	$115.36	$115.35	$115.40
Purchase #3	$86.97	10.868%	$96.4219	$96.42	$96.40	$96.40
Purchase #4	$82.30	9.852%	$90.4082	$90.41	$90.40	$90.40
Purchase #5	$38.83	6.221%	$41.2456	$41.25	$41.25	$41.20
Purchase #6	$78.31	9.363%	$85.6422	$85.64	$85.65	$85.60
Purchase #7	$91.48	8.464%	$99.2229	$99.22	$99.20	$99.20
7 purchase totals =	$675.00		$739.9995	$740.00	$739.95	$739.90