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	$123.59	10.812%	$136.9526	$136.95	$136.95	$137.00
Purchase #2	$177.72	10.322%	$196.0643	$196.06	$196.05	$196.10
Purchase #3	$50.29	4.831%	$52.7195	$52.72	$52.70	$52.70
Purchase #4	$19.61	4.732%	$20.5379	$20.54	$20.55	$20.50
Purchase #5	$213.58	10.345%	$235.6749	$235.67	$235.65	$235.70
Purchase #6	$102.34	3.575%	$105.9987	$106.00	$106.00	$106.00
Purchase #7	$174.29	11.459%	$194.2619	$194.26	$194.25	$194.30
7 purchase totals =	$861.42		$942.2098	$942.20	$942.15	$942.30