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	$118.89	9.200%	$129.8279	$129.83	$129.85	$129.80
Purchase #2	$175.95	8.721%	$191.2946	$191.29	$191.30	$191.30
Purchase #3	$23.30	8.469%	$25.2733	$25.27	$25.25	$25.30
Purchase #4	$238.99	4.787%	$250.4305	$250.43	$250.45	$250.40
Purchase #5	$119.82	9.358%	$131.0328	$131.03	$131.05	$131.00
Purchase #6	$188.98	6.129%	$200.5626	$200.56	$200.55	$200.60
Purchase #7	$125.76	13.524%	$142.7678	$142.77	$142.75	$142.80
7 purchase totals =	$991.69		$1,071.1895	$1,071.18	$1,071.20	$1,071.20