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	$151.64	4.399%	$158.3106	$158.31	$158.30	$158.30
Purchase #2	$175.32	4.314%	$182.8833	$182.88	$182.90	$182.90
Purchase #3	$183.33	4.374%	$191.3489	$191.35	$191.35	$191.30
Purchase #4	$31.85	3.429%	$32.9421	$32.94	$32.95	$32.90
Purchase #5	$48.53	6.223%	$51.55	$51.55	$51.55	$51.60
Purchase #6	$160.96	8.627%	$174.846	$174.85	$174.85	$174.80
Purchase #7	$241.87	11.823%	$270.4663	$270.47	$270.45	$270.50
7 purchase totals =	$993.50		$1,062.3472	$1,062.35	$1,062.35	$1,062.30