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	$134.99	5.721%	$142.7128	$142.71	$142.70	$142.70
Purchase #2	$171.95	10.581%	$190.144	$190.14	$190.15	$190.10
Purchase #3	$136.25	6.690%	$145.3651	$145.37	$145.35	$145.40
Purchase #4	$70.80	4.271%	$73.8239	$73.82	$73.80	$73.80
Purchase #5	$224.35	11.542%	$250.2445	$250.24	$250.25	$250.20
Purchase #6	$192.69	3.228%	$198.91	$198.91	$198.90	$198.90
Purchase #7	$133.32	7.497%	$143.315	$143.32	$143.30	$143.30
7 purchase totals =	$1,064.35		$1,144.5153	$1,144.51	$1,144.45	$1,144.40