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	$168.36	6.600%	$179.4718	$179.47	$179.45	$179.50
Purchase #2	$35.55	4.664%	$37.2081	$37.21	$37.20	$37.20
Purchase #3	$113.37	12.822%	$127.9063	$127.91	$127.90	$127.90
Purchase #4	$192.57	7.185%	$206.4062	$206.41	$206.40	$206.40
Purchase #5	$191.40	10.749%	$211.9736	$211.97	$211.95	$212.00
Purchase #6	$94.51	8.638%	$102.6738	$102.67	$102.65	$102.70
Purchase #7	$233.48	4.345%	$243.6247	$243.62	$243.60	$243.60
7 purchase totals =	$1,029.24		$1,109.2645	$1,109.26	$1,109.15	$1,109.30