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	$174.76	3.543%	$180.9517	$180.95	$180.95	$181.00
Purchase #2	$99.84	10.413%	$110.2363	$110.24	$110.25	$110.20
Purchase #3	$75.64	9.450%	$82.788	$82.79	$82.80	$82.80
Purchase #4	$73.42	12.839%	$82.8464	$82.85	$82.85	$82.80
Purchase #5	$172.83	5.167%	$181.7601	$181.76	$181.75	$181.80
Purchase #6	$196.56	4.239%	$204.8922	$204.89	$204.90	$204.90
Purchase #7	$10.58	4.437%	$11.0494	$11.05	$11.05	$11.00
7 purchase totals =	$803.63		$854.5241	$854.53	$854.55	$854.50