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	$60.33	3.145%	$62.2274	$62.23	$62.25	$62.20
Purchase #2	$249.37	7.527%	$268.1401	$268.14	$268.15	$268.10
Purchase #3	$215.90	6.504%	$229.9421	$229.94	$229.95	$229.90
Purchase #4	$125.58	12.682%	$141.5061	$141.51	$141.50	$141.50
Purchase #5	$177.28	13.322%	$200.8972	$200.90	$200.90	$200.90
Purchase #6	$81.83	11.298%	$91.0752	$91.08	$91.10	$91.10
Purchase #7	$105.81	9.208%	$115.553	$115.55	$115.55	$115.60
7 purchase totals =	$1,016.10		$1,109.3411	$1,109.35	$1,109.40	$1,109.30