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	$100.91	11.829%	$112.8466	$112.85	$112.85	$112.80
Purchase #2	$148.31	3.568%	$153.6017	$153.60	$153.60	$153.60
Purchase #3	$41.52	5.708%	$43.89	$43.89	$43.90	$43.90
Purchase #4	$231.41	13.787%	$263.3145	$263.31	$263.30	$263.30
Purchase #5	$105.81	13.782%	$120.3927	$120.39	$120.40	$120.40
Purchase #6	$182.93	9.166%	$199.6974	$199.70	$199.70	$199.70
Purchase #7	$248.99	7.784%	$268.3714	$268.37	$268.35	$268.40
7 purchase totals =	$1,059.88		$1,162.1143	$1,162.11	$1,162.10	$1,162.10