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	$110.66	11.405%	$123.2808	$123.28	$123.30	$123.30
Purchase #2	$41.75	12.560%	$46.9938	$46.99	$47.00	$47.00
Purchase #3	$52.81	3.736%	$54.783	$54.78	$54.80	$54.80
Purchase #4	$155.85	9.118%	$170.0604	$170.06	$170.05	$170.10
Purchase #5	$143.56	6.457%	$152.8297	$152.83	$152.85	$152.80
Purchase #6	$105.67	8.770%	$114.9373	$114.94	$114.95	$114.90
Purchase #7	$96.59	11.381%	$107.5829	$107.58	$107.60	$107.60
7 purchase totals =	$706.89		$770.4679	$770.46	$770.55	$770.50