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	$76.73	7.409%	$82.4149	$82.41	$82.40	$82.40
Purchase #2	$103.28	6.481%	$109.9736	$109.97	$109.95	$110.00
Purchase #3	$158.34	4.151%	$164.9127	$164.91	$164.90	$164.90
Purchase #4	$116.47	9.631%	$127.6872	$127.69	$127.70	$127.70
Purchase #5	$136.67	11.478%	$152.357	$152.36	$152.35	$152.40
Purchase #6	$32.73	10.139%	$36.0485	$36.05	$36.05	$36.00
Purchase #7	$119.72	6.537%	$127.5461	$127.55	$127.55	$127.50
7 purchase totals =	$743.94		$800.9400	$800.94	$800.90	$800.90