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	$227.46	12.114%	$255.0145	$255.01	$255.00	$255.00
Purchase #2	$213.52	13.696%	$242.7637	$242.76	$242.75	$242.80
Purchase #3	$64.89	3.463%	$67.1371	$67.14	$67.15	$67.10
Purchase #4	$112.79	3.110%	$116.2978	$116.30	$116.30	$116.30
Purchase #5	$41.71	12.681%	$46.9992	$47.00	$47.00	$47.00
Purchase #6	$97.41	9.641%	$106.8013	$106.80	$106.80	$106.80
Purchase #7	$147.92	12.834%	$166.9041	$166.90	$166.90	$166.90
7 purchase totals =	$905.70		$1,001.9177	$1,001.91	$1,001.90	$1,001.90