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	$58.97	3.524%	$61.0481	$61.05	$61.05	$61.00
Purchase #2	$80.75	12.541%	$90.8769	$90.88	$90.90	$90.90
Purchase #3	$11.33	8.621%	$12.3068	$12.31	$12.30	$12.30
Purchase #4	$240.83	3.631%	$249.5745	$249.57	$249.55	$249.60
Purchase #5	$250.25	3.331%	$258.5858	$258.59	$258.60	$258.60
Purchase #6	$43.63	3.540%	$45.1745	$45.17	$45.15	$45.20
Purchase #7	$80.70	8.408%	$87.4853	$87.49	$87.50	$87.50
7 purchase totals =	$766.46		$805.0519	$805.06	$805.05	$805.10