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	$169.37	8.556%	$183.8613	$183.86	$183.85	$183.90
Purchase #2	$136.52	10.581%	$150.9652	$150.97	$150.95	$151.00
Purchase #3	$19.33	8.289%	$20.9323	$20.93	$20.95	$20.90
Purchase #4	$10.46	6.133%	$11.1015	$11.10	$11.10	$11.10
Purchase #5	$163.96	6.208%	$174.1386	$174.14	$174.15	$174.10
Purchase #6	$86.78	3.301%	$89.6446	$89.64	$89.65	$89.60
Purchase #7	$50.28	9.792%	$55.2034	$55.20	$55.20	$55.20
7 purchase totals =	$636.70		$685.8469	$685.84	$685.85	$685.80