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	$100.75	10.539%	$111.368	$111.37	$111.35	$111.40
Purchase #2	$154.58	11.356%	$172.1341	$172.13	$172.15	$172.10
Purchase #3	$178.46	11.461%	$198.9133	$198.91	$198.90	$198.90
Purchase #4	$162.87	3.410%	$168.4239	$168.42	$168.40	$168.40
Purchase #5	$176.95	13.351%	$200.5746	$200.57	$200.55	$200.60
Purchase #6	$172.84	9.587%	$189.4102	$189.41	$189.40	$189.40
Purchase #7	$137.92	9.349%	$150.8141	$150.81	$150.80	$150.80
7 purchase totals =	$1,084.37		$1,191.6382	$1,191.62	$1,191.55	$1,191.60