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	$206.93	8.793%	$225.1254	$225.13	$225.15	$225.10
Purchase #2	$171.82	5.763%	$181.722	$181.72	$181.70	$181.70
Purchase #3	$114.54	5.104%	$120.3861	$120.39	$120.40	$120.40
Purchase #4	$155.25	10.788%	$171.9984	$172.00	$172.00	$172.00
Purchase #5	$82.55	10.275%	$91.032	$91.03	$91.05	$91.00
Purchase #6	$86.76	4.586%	$90.7388	$90.74	$90.75	$90.70
Purchase #7	$158.58	5.573%	$167.4177	$167.42	$167.40	$167.40
7 purchase totals =	$976.43		$1,048.4204	$1,048.43	$1,048.45	$1,048.30