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	$127.29	11.468%	$141.8876	$141.89	$141.90	$141.90
Purchase #2	$141.73	11.864%	$158.5448	$158.54	$158.55	$158.50
Purchase #3	$232.39	3.418%	$240.3331	$240.33	$240.35	$240.30
Purchase #4	$196.36	9.552%	$215.1163	$215.12	$215.10	$215.10
Purchase #5	$27.86	3.139%	$28.7345	$28.73	$28.75	$28.70
Purchase #6	$57.84	12.605%	$65.1307	$65.13	$65.15	$65.10
Purchase #7	$190.41	10.398%	$210.2088	$210.21	$210.20	$210.20
7 purchase totals =	$973.88		$1,059.9558	$1,059.95	$1,060.00	$1,059.80