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	$174.28	11.603%	$194.5017	$194.50	$194.50	$194.50
Purchase #2	$109.38	12.802%	$123.3828	$123.38	$123.40	$123.40
Purchase #3	$104.53	4.339%	$109.0656	$109.07	$109.05	$109.10
Purchase #4	$53.97	9.573%	$59.1365	$59.14	$59.15	$59.10
Purchase #5	$125.51	10.682%	$138.917	$138.92	$138.90	$138.90
Purchase #6	$183.25	4.669%	$191.8059	$191.81	$191.80	$191.80
Purchase #7	$160.29	6.761%	$171.1272	$171.13	$171.15	$171.10
7 purchase totals =	$911.21		$987.9367	$987.95	$987.95	$987.90