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	$218.52	13.659%	$248.3676	$248.37	$248.35	$248.40
Purchase #2	$36.38	12.231%	$40.8296	$40.83	$40.85	$40.80
Purchase #3	$76.31	8.499%	$82.7956	$82.80	$82.80	$82.80
Purchase #4	$54.85	7.661%	$59.0521	$59.05	$59.05	$59.10
Purchase #5	$139.53	10.216%	$153.7844	$153.78	$153.80	$153.80
Purchase #6	$129.29	4.512%	$135.1236	$135.12	$135.10	$135.10
Purchase #7	$160.98	7.769%	$173.4865	$173.49	$173.50	$173.50
7 purchase totals =	$815.86		$893.4394	$893.44	$893.45	$893.50