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	$184.93	3.524%	$191.4469	$191.45	$191.45	$191.40
Purchase #2	$162.40	10.710%	$179.793	$179.79	$179.80	$179.80
Purchase #3	$207.54	11.365%	$231.1269	$231.13	$231.15	$231.10
Purchase #4	$69.66	7.507%	$74.8894	$74.89	$74.90	$74.90
Purchase #5	$235.77	12.176%	$264.4774	$264.48	$264.50	$264.50
Purchase #6	$126.86	12.805%	$143.1044	$143.10	$143.10	$143.10
Purchase #7	$57.61	8.462%	$62.485	$62.49	$62.50	$62.50
7 purchase totals =	$1,044.77		$1,147.3230	$1,147.33	$1,147.40	$1,147.30