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	$150.97	3.695%	$156.5483	$156.55	$156.55	$156.50
Purchase #2	$5.85	12.669%	$6.5911	$6.59	$6.60	$6.60
Purchase #3	$200.32	4.369%	$209.072	$209.07	$209.05	$209.10
Purchase #4	$181.33	7.141%	$194.2788	$194.28	$194.30	$194.30
Purchase #5	$57.59	8.152%	$62.2847	$62.28	$62.30	$62.30
Purchase #6	$243.78	4.215%	$254.0553	$254.06	$254.05	$254.10
Purchase #7	$109.77	6.463%	$116.8644	$116.86	$116.85	$116.90
7 purchase totals =	$949.61		$999.6946	$999.69	$999.70	$999.80