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	$182.59	13.643%	$207.5008	$207.50	$207.50	$207.50
Purchase #2	$33.45	7.333%	$35.9029	$35.90	$35.90	$35.90
Purchase #3	$194.94	5.225%	$205.1256	$205.13	$205.15	$205.10
Purchase #4	$82.33	8.179%	$89.0638	$89.06	$89.05	$89.10
Purchase #5	$231.30	10.387%	$255.3251	$255.33	$255.35	$255.30
Purchase #6	$232.31	4.279%	$242.2505	$242.25	$242.25	$242.30
Purchase #7	$137.62	13.487%	$156.1808	$156.18	$156.20	$156.20
7 purchase totals =	$1,094.54		$1,191.3495	$1,191.35	$1,191.40	$1,191.40