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	$152.78	10.202%	$168.3666	$168.37	$168.35	$168.40
Purchase #2	$127.33	11.556%	$142.0443	$142.04	$142.05	$142.00
Purchase #3	$122.56	8.788%	$133.3306	$133.33	$133.35	$133.30
Purchase #4	$167.39	3.648%	$173.4964	$173.50	$173.50	$173.50
Purchase #5	$162.28	10.379%	$179.123	$179.12	$179.10	$179.10
Purchase #6	$167.81	9.502%	$183.7553	$183.76	$183.75	$183.80
Purchase #7	$133.54	5.819%	$141.3107	$141.31	$141.30	$141.30
7 purchase totals =	$1,033.69		$1,121.4269	$1,121.43	$1,121.40	$1,121.40