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	$158.41	10.674%	$175.3187	$175.32	$175.30	$175.30
Purchase #2	$150.91	10.568%	$166.8582	$166.86	$166.85	$166.90
Purchase #3	$155.73	8.108%	$168.3566	$168.36	$168.35	$168.40
Purchase #4	$69.75	12.429%	$78.4192	$78.42	$78.40	$78.40
Purchase #5	$123.92	9.315%	$135.4631	$135.46	$135.45	$135.50
Purchase #6	$71.76	4.316%	$74.8572	$74.86	$74.85	$74.90
Purchase #7	$78.32	8.786%	$85.2012	$85.20	$85.20	$85.20
7 purchase totals =	$808.80		$884.4742	$884.48	$884.40	$884.60