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	$40.90	11.296%	$45.5201	$45.52	$45.50	$45.50
Purchase #2	$165.36	12.258%	$185.6298	$185.63	$185.65	$185.60
Purchase #3	$218.40	6.418%	$232.4169	$232.42	$232.40	$232.40
Purchase #4	$114.38	7.741%	$123.2342	$123.23	$123.25	$123.20
Purchase #5	$119.33	7.159%	$127.8728	$127.87	$127.85	$127.90
Purchase #6	$178.87	11.284%	$199.0537	$199.05	$199.05	$199.10
Purchase #7	$19.65	12.714%	$22.1483	$22.15	$22.15	$22.10
7 purchase totals =	$856.89		$935.8758	$935.87	$935.85	$935.80