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	$114.54	3.423%	$118.4607	$118.46	$118.45	$118.50
Purchase #2	$176.92	3.678%	$183.4271	$183.43	$183.45	$183.40
Purchase #3	$72.49	6.223%	$77.0011	$77.00	$77.00	$77.00
Purchase #4	$83.45	6.695%	$89.037	$89.04	$89.05	$89.00
Purchase #5	$180.41	4.174%	$187.9403	$187.94	$187.95	$187.90
Purchase #6	$137.34	7.567%	$147.7325	$147.73	$147.75	$147.70
Purchase #7	$92.56	5.872%	$97.9951	$98.00	$98.00	$98.00
7 purchase totals =	$857.71		$901.5938	$901.60	$901.65	$901.50