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	$148.31	13.683%	$168.6033	$168.60	$168.60	$168.60
Purchase #2	$115.56	9.801%	$126.886	$126.89	$126.90	$126.90
Purchase #3	$89.60	10.800%	$99.2768	$99.28	$99.30	$99.30
Purchase #4	$95.84	8.289%	$103.7842	$103.78	$103.80	$103.80
Purchase #5	$194.29	13.617%	$220.7465	$220.75	$220.75	$220.70
Purchase #6	$173.67	6.112%	$184.2847	$184.28	$184.30	$184.30
Purchase #7	$215.27	9.471%	$235.6582	$235.66	$235.65	$235.70
7 purchase totals =	$1,032.54		$1,139.2397	$1,139.24	$1,139.30	$1,139.30