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	$111.76	6.459%	$118.9786	$118.98	$119.00	$119.00
Purchase #2	$145.83	11.475%	$162.564	$162.56	$162.55	$162.60
Purchase #3	$82.31	11.740%	$91.9732	$91.97	$91.95	$92.00
Purchase #4	$204.73	10.309%	$225.8356	$225.84	$225.85	$225.80
Purchase #5	$72.70	11.483%	$81.0481	$81.05	$81.05	$81.00
Purchase #6	$108.43	11.152%	$120.5221	$120.52	$120.50	$120.50
Purchase #7	$80.47	5.821%	$85.1542	$85.15	$85.15	$85.20
7 purchase totals =	$806.23		$886.0758	$886.07	$886.05	$886.10