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	$136.64	11.211%	$151.9587	$151.96	$151.95	$152.00
Purchase #2	$236.37	10.553%	$261.3141	$261.31	$261.30	$261.30
Purchase #3	$133.84	3.865%	$139.0129	$139.01	$139.00	$139.00
Purchase #4	$85.28	7.401%	$91.5916	$91.59	$91.60	$91.60
Purchase #5	$51.47	9.834%	$56.5316	$56.53	$56.55	$56.50
Purchase #6	$135.39	7.550%	$145.6119	$145.61	$145.60	$145.60
Purchase #7	$145.87	8.694%	$158.5519	$158.55	$158.55	$158.60
7 purchase totals =	$924.86		$1,004.5727	$1,004.56	$1,004.55	$1,004.60