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	$245.86	3.751%	$255.0822	$255.08	$255.10	$255.10
Purchase #2	$155.38	4.472%	$162.3286	$162.33	$162.35	$162.30
Purchase #3	$21.83	4.823%	$22.8829	$22.88	$22.90	$22.90
Purchase #4	$97.96	6.260%	$104.0923	$104.09	$104.10	$104.10
Purchase #5	$214.35	11.238%	$238.4387	$238.44	$238.45	$238.40
Purchase #6	$30.38	5.429%	$32.0293	$32.03	$32.05	$32.00
Purchase #7	$93.41	11.223%	$103.8934	$103.89	$103.90	$103.90
7 purchase totals =	$859.17		$918.7474	$918.74	$918.85	$918.70