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	$103.96	7.245%	$111.4919	$111.49	$111.50	$111.50
Purchase #2	$95.33	12.731%	$107.4665	$107.47	$107.45	$107.50
Purchase #3	$146.49	13.150%	$165.7534	$165.75	$165.75	$165.80
Purchase #4	$170.65	8.433%	$185.0409	$185.04	$185.05	$185.00
Purchase #5	$101.69	13.477%	$115.3948	$115.39	$115.40	$115.40
Purchase #6	$237.52	5.304%	$250.1181	$250.12	$250.10	$250.10
Purchase #7	$84.81	7.370%	$91.0605	$91.06	$91.05	$91.10
7 purchase totals =	$940.45		$1,026.3261	$1,026.32	$1,026.30	$1,026.40