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	$180.99	10.161%	$199.3804	$199.38	$199.40	$199.40
Purchase #2	$181.81	10.400%	$200.7182	$200.72	$200.70	$200.70
Purchase #3	$192.50	4.280%	$200.739	$200.74	$200.75	$200.70
Purchase #4	$202.57	11.243%	$225.3449	$225.34	$225.35	$225.30
Purchase #5	$54.92	10.256%	$60.5526	$60.55	$60.55	$60.60
Purchase #6	$26.46	4.790%	$27.7274	$27.73	$27.75	$27.70
Purchase #7	$82.66	10.153%	$91.0525	$91.05	$91.05	$91.10
7 purchase totals =	$921.91		$1,005.5150	$1,005.51	$1,005.55	$1,005.50