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	$229.62	9.274%	$250.915	$250.92	$250.90	$250.90
Purchase #2	$35.86	5.801%	$37.9402	$37.94	$37.95	$37.90
Purchase #3	$78.65	5.694%	$83.1283	$83.13	$83.15	$83.10
Purchase #4	$246.88	4.125%	$257.0638	$257.06	$257.05	$257.10
Purchase #5	$115.54	6.731%	$123.317	$123.32	$123.30	$123.30
Purchase #6	$30.62	7.159%	$32.8121	$32.81	$32.80	$32.80
Purchase #7	$18.34	7.284%	$19.6759	$19.68	$19.70	$19.70
7 purchase totals =	$755.51		$804.8523	$804.86	$804.85	$804.80