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	$214.51	12.259%	$240.8068	$240.81	$240.80	$240.80
Purchase #2	$53.75	3.776%	$55.7796	$55.78	$55.80	$55.80
Purchase #3	$24.81	4.322%	$25.8823	$25.88	$25.90	$25.90
Purchase #4	$154.90	4.153%	$161.333	$161.33	$161.35	$161.30
Purchase #5	$134.54	13.490%	$152.6894	$152.69	$152.70	$152.70
Purchase #6	$178.74	6.609%	$190.5529	$190.55	$190.55	$190.60
Purchase #7	$176.36	8.407%	$191.1866	$191.19	$191.20	$191.20
7 purchase totals =	$937.61		$1,018.2306	$1,018.23	$1,018.30	$1,018.30