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	$115.68	11.794%	$129.3233	$129.32	$129.30	$129.30
Purchase #2	$145.94	8.480%	$158.3157	$158.32	$158.30	$158.30
Purchase #3	$123.32	6.828%	$131.7403	$131.74	$131.75	$131.70
Purchase #4	$72.45	8.530%	$78.63	$78.63	$78.65	$78.60
Purchase #5	$165.25	12.339%	$185.6402	$185.64	$185.65	$185.60
Purchase #6	$198.40	3.210%	$204.7686	$204.77	$204.75	$204.80
Purchase #7	$165.85	12.247%	$186.1616	$186.16	$186.15	$186.20
7 purchase totals =	$986.89		$1,074.5797	$1,074.58	$1,074.55	$1,074.50