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	$136.39	4.874%	$143.0376	$143.04	$143.05	$143.00
Purchase #2	$244.81	4.537%	$255.917	$255.92	$255.90	$255.90
Purchase #3	$54.79	10.673%	$60.6377	$60.64	$60.65	$60.60
Purchase #4	$136.94	7.678%	$147.4543	$147.45	$147.45	$147.50
Purchase #5	$39.59	3.568%	$41.0026	$41.00	$41.00	$41.00
Purchase #6	$29.68	5.783%	$31.3964	$31.40	$31.40	$31.40
Purchase #7	$222.69	11.718%	$248.7848	$248.78	$248.80	$248.80
7 purchase totals =	$864.89		$928.2304	$928.23	$928.25	$928.20