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	$168.72	10.617%	$186.633	$186.63	$186.65	$186.60
Purchase #2	$54.90	9.218%	$59.9607	$59.96	$59.95	$60.00
Purchase #3	$166.59	11.840%	$186.3143	$186.31	$186.30	$186.30
Purchase #4	$25.37	10.303%	$27.9839	$27.98	$28.00	$28.00
Purchase #5	$12.47	13.204%	$14.1165	$14.12	$14.10	$14.10
Purchase #6	$110.41	8.191%	$119.4537	$119.45	$119.45	$119.50
Purchase #7	$93.43	10.407%	$103.1533	$103.15	$103.15	$103.20
7 purchase totals =	$631.89		$697.6154	$697.60	$697.60	$697.70