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	$204.33	7.854%	$220.3781	$220.38	$220.40	$220.40
Purchase #2	$86.95	9.526%	$95.2329	$95.23	$95.25	$95.20
Purchase #3	$240.76	11.461%	$268.3535	$268.35	$268.35	$268.40
Purchase #4	$111.49	3.524%	$115.4189	$115.42	$115.40	$115.40
Purchase #5	$200.97	10.510%	$222.0919	$222.09	$222.10	$222.10
Purchase #6	$46.46	13.199%	$52.5923	$52.59	$52.60	$52.60
Purchase #7	$166.46	13.219%	$188.4643	$188.46	$188.45	$188.50
7 purchase totals =	$1,057.42		$1,162.5319	$1,162.52	$1,162.55	$1,162.60