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	$136.34	9.336%	$149.0687	$149.07	$149.05	$149.10
Purchase #2	$69.84	3.111%	$72.0127	$72.01	$72.00	$72.00
Purchase #3	$142.82	13.460%	$162.0436	$162.04	$162.05	$162.00
Purchase #4	$248.96	10.568%	$275.2701	$275.27	$275.25	$275.30
Purchase #5	$99.50	10.107%	$109.5565	$109.56	$109.55	$109.60
Purchase #6	$129.74	9.447%	$141.9965	$142.00	$142.00	$142.00
Purchase #7	$115.68	13.615%	$131.4298	$131.43	$131.45	$131.40
7 purchase totals =	$942.88		$1,041.3779	$1,041.38	$1,041.35	$1,041.40