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	$63.42	13.410%	$71.9246	$71.92	$71.90	$71.90
Purchase #2	$142.90	5.575%	$150.8667	$150.87	$150.85	$150.90
Purchase #3	$222.72	5.507%	$234.9852	$234.99	$235.00	$235.00
Purchase #4	$154.36	10.412%	$170.432	$170.43	$170.45	$170.40
Purchase #5	$92.25	12.663%	$103.9316	$103.93	$103.95	$103.90
Purchase #6	$78.38	3.870%	$81.4133	$81.41	$81.40	$81.40
Purchase #7	$193.75	6.781%	$206.8882	$206.89	$206.90	$206.90
7 purchase totals =	$947.78		$1,020.4416	$1,020.44	$1,020.45	$1,020.40