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	$103.68	13.124%	$117.287	$117.29	$117.30	$117.30
Purchase #2	$209.89	6.501%	$223.5349	$223.53	$223.55	$223.50
Purchase #3	$186.61	12.727%	$210.3599	$210.36	$210.35	$210.40
Purchase #4	$87.76	12.320%	$98.572	$98.57	$98.55	$98.60
Purchase #5	$73.62	5.483%	$77.6566	$77.66	$77.65	$77.70
Purchase #6	$164.85	13.315%	$186.7998	$186.80	$186.80	$186.80
Purchase #7	$92.55	11.477%	$103.172	$103.17	$103.15	$103.20
7 purchase totals =	$918.96		$1,017.3822	$1,017.38	$1,017.35	$1,017.50