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	$114.88	9.411%	$125.6914	$125.69	$125.70	$125.70
Purchase #2	$55.58	7.216%	$59.5907	$59.59	$59.60	$59.60
Purchase #3	$171.85	6.545%	$183.0976	$183.10	$183.10	$183.10
Purchase #4	$155.76	4.262%	$162.3985	$162.40	$162.40	$162.40
Purchase #5	$193.71	11.202%	$215.4094	$215.41	$215.40	$215.40
Purchase #6	$225.75	10.545%	$249.5553	$249.56	$249.55	$249.60
Purchase #7	$142.85	9.586%	$156.5436	$156.54	$156.55	$156.50
7 purchase totals =	$1,060.38		$1,152.2865	$1,152.29	$1,152.30	$1,152.30