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	$129.77	10.753%	$143.7242	$143.72	$143.70	$143.70
Purchase #2	$28.40	10.765%	$31.4573	$31.46	$31.45	$31.50
Purchase #3	$185.50	13.512%	$210.5648	$210.56	$210.55	$210.60
Purchase #4	$181.67	7.210%	$194.7684	$194.77	$194.75	$194.80
Purchase #5	$127.62	5.393%	$134.5025	$134.50	$134.50	$134.50
Purchase #6	$27.49	13.786%	$31.2798	$31.28	$31.30	$31.30
Purchase #7	$39.63	7.611%	$42.6462	$42.65	$42.65	$42.60
7 purchase totals =	$720.08		$788.9432	$788.94	$788.90	$789.00