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	$200.34	5.577%	$211.513	$211.51	$211.50	$211.50
Purchase #2	$224.75	4.449%	$234.7491	$234.75	$234.75	$234.70
Purchase #3	$33.89	12.409%	$38.0954	$38.10	$38.10	$38.10
Purchase #4	$106.74	3.860%	$110.8602	$110.86	$110.85	$110.90
Purchase #5	$178.41	5.872%	$188.8862	$188.89	$188.90	$188.90
Purchase #6	$100.68	10.172%	$110.9212	$110.92	$110.90	$110.90
Purchase #7	$140.55	4.145%	$146.3758	$146.38	$146.40	$146.40
7 purchase totals =	$985.36		$1,041.4009	$1,041.41	$1,041.40	$1,041.40