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	$215.54	12.803%	$243.1356	$243.14	$243.15	$243.10
Purchase #2	$56.35	4.852%	$59.0841	$59.08	$59.10	$59.10
Purchase #3	$66.52	3.385%	$68.7717	$68.77	$68.75	$68.80
Purchase #4	$105.92	3.236%	$109.3476	$109.35	$109.35	$109.30
Purchase #5	$221.81	7.173%	$237.7204	$237.72	$237.70	$237.70
Purchase #6	$248.86	13.118%	$281.5055	$281.51	$281.50	$281.50
Purchase #7	$24.72	10.175%	$27.2353	$27.24	$27.25	$27.20
7 purchase totals =	$939.72		$1,026.8002	$1,026.81	$1,026.80	$1,026.70