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	$41.80	4.643%	$43.7408	$43.74	$43.75	$43.70
Purchase #2	$222.83	12.597%	$250.8999	$250.90	$250.90	$250.90
Purchase #3	$161.72	4.670%	$169.2723	$169.27	$169.25	$169.30
Purchase #4	$214.72	6.270%	$228.1829	$228.18	$228.20	$228.20
Purchase #5	$157.36	3.539%	$162.929	$162.93	$162.95	$162.90
Purchase #6	$60.85	12.110%	$68.2189	$68.22	$68.20	$68.20
Purchase #7	$170.78	10.309%	$188.3857	$188.39	$188.40	$188.40
7 purchase totals =	$1,030.06		$1,111.6295	$1,111.63	$1,111.65	$1,111.60