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	$226.72	4.348%	$236.5778	$236.58	$236.60	$236.60
Purchase #2	$88.80	5.531%	$93.7115	$93.71	$93.70	$93.70
Purchase #3	$45.54	4.295%	$47.4959	$47.50	$47.50	$47.50
Purchase #4	$250.76	11.809%	$280.3722	$280.37	$280.35	$280.40
Purchase #5	$79.69	13.439%	$90.3995	$90.40	$90.40	$90.40
Purchase #6	$119.36	11.694%	$133.318	$133.32	$133.30	$133.30
Purchase #7	$162.73	3.348%	$168.1782	$168.18	$168.20	$168.20
7 purchase totals =	$973.60		$1,050.0531	$1,050.06	$1,050.05	$1,050.10