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	$83.66	11.142%	$92.9814	$92.98	$93.00	$93.00
Purchase #2	$169.90	10.623%	$187.9485	$187.95	$187.95	$187.90
Purchase #3	$102.91	7.807%	$110.9442	$110.94	$110.95	$110.90
Purchase #4	$178.81	9.823%	$196.3745	$196.37	$196.35	$196.40
Purchase #5	$173.87	6.403%	$185.0029	$185.00	$185.00	$185.00
Purchase #6	$248.69	10.597%	$275.0437	$275.04	$275.05	$275.00
Purchase #7	$51.33	7.553%	$55.207	$55.21	$55.20	$55.20
7 purchase totals =	$1,009.17		$1,103.5022	$1,103.49	$1,103.50	$1,103.40