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	$42.71	9.618%	$46.8178	$46.82	$46.80	$46.80
Purchase #2	$96.69	3.811%	$100.3749	$100.37	$100.35	$100.40
Purchase #3	$91.31	13.770%	$103.8834	$103.88	$103.90	$103.90
Purchase #4	$115.88	13.645%	$131.6918	$131.69	$131.70	$131.70
Purchase #5	$18.46	3.262%	$19.0622	$19.06	$19.05	$19.10
Purchase #6	$100.59	7.678%	$108.3133	$108.31	$108.30	$108.30
Purchase #7	$97.61	5.578%	$103.0547	$103.05	$103.05	$103.10
7 purchase totals =	$563.25		$613.1981	$613.18	$613.15	$613.30