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	$212.30	9.778%	$233.0587	$233.06	$233.05	$233.10
Purchase #2	$176.91	11.246%	$196.8053	$196.81	$196.80	$196.80
Purchase #3	$164.64	10.747%	$182.3339	$182.33	$182.35	$182.30
Purchase #4	$137.72	10.591%	$152.3059	$152.31	$152.30	$152.30
Purchase #5	$25.59	12.294%	$28.736	$28.74	$28.75	$28.70
Purchase #6	$16.93	13.269%	$19.1764	$19.18	$19.20	$19.20
Purchase #7	$121.38	7.491%	$130.4726	$130.47	$130.45	$130.50
7 purchase totals =	$855.47		$942.8888	$942.90	$942.90	$942.90