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	$20.62	4.749%	$21.5992	$21.60	$21.60	$21.60
Purchase #2	$214.33	10.549%	$236.9397	$236.94	$236.95	$236.90
Purchase #3	$177.73	10.301%	$196.038	$196.04	$196.05	$196.00
Purchase #4	$221.69	4.688%	$232.0828	$232.08	$232.10	$232.10
Purchase #5	$248.46	10.808%	$275.3136	$275.31	$275.30	$275.30
Purchase #6	$165.59	8.704%	$180.003	$180.00	$180.00	$180.00
Purchase #7	$19.81	5.548%	$20.9091	$20.91	$20.90	$20.90
7 purchase totals =	$1,068.23		$1,162.8854	$1,162.88	$1,162.90	$1,162.80