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	$82.68	6.870%	$88.3601	$88.36	$88.35	$88.40
Purchase #2	$83.46	7.230%	$89.4942	$89.49	$89.50	$89.50
Purchase #3	$244.55	3.247%	$252.4905	$252.49	$252.50	$252.50
Purchase #4	$212.39	13.111%	$240.2365	$240.24	$240.25	$240.20
Purchase #5	$96.33	13.336%	$109.1766	$109.18	$109.20	$109.20
Purchase #6	$152.35	8.522%	$165.3333	$165.33	$165.35	$165.30
Purchase #7	$56.62	7.450%	$60.8382	$60.84	$60.85	$60.80
7 purchase totals =	$928.38		$1,005.9294	$1,005.93	$1,006.00	$1,005.90