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	$179.69	6.473%	$191.3213	$191.32	$191.30	$191.30
Purchase #2	$81.46	11.295%	$90.6609	$90.66	$90.65	$90.70
Purchase #3	$53.54	5.135%	$56.2893	$56.29	$56.30	$56.30
Purchase #4	$185.53	10.318%	$204.673	$204.67	$204.65	$204.70
Purchase #5	$246.89	3.371%	$255.2127	$255.21	$255.20	$255.20
Purchase #6	$54.49	11.662%	$60.8446	$60.84	$60.85	$60.80
Purchase #7	$191.88	12.808%	$216.456	$216.46	$216.45	$216.50
7 purchase totals =	$993.48		$1,075.4578	$1,075.45	$1,075.40	$1,075.50