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	$181.95	3.182%	$187.7396	$187.74	$187.75	$187.70
Purchase #2	$119.68	9.760%	$131.3608	$131.36	$131.35	$131.40
Purchase #3	$119.28	7.220%	$127.892	$127.89	$127.90	$127.90
Purchase #4	$39.98	10.657%	$44.2407	$44.24	$44.25	$44.20
Purchase #5	$212.89	5.202%	$223.9645	$223.96	$223.95	$224.00
Purchase #6	$248.63	3.292%	$256.8149	$256.81	$256.80	$256.80
Purchase #7	$67.46	11.584%	$75.2746	$75.27	$75.25	$75.30
7 purchase totals =	$989.87		$1,047.2871	$1,047.27	$1,047.25	$1,047.30