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	$39.63	10.791%	$43.9065	$43.91	$43.90	$43.90
Purchase #2	$56.33	9.179%	$61.5005	$61.50	$61.50	$61.50
Purchase #3	$58.89	6.658%	$62.8109	$62.81	$62.80	$62.80
Purchase #4	$112.99	4.867%	$118.4892	$118.49	$118.50	$118.50
Purchase #5	$172.86	3.850%	$179.5151	$179.52	$179.50	$179.50
Purchase #6	$49.34	13.263%	$55.884	$55.88	$55.90	$55.90
Purchase #7	$244.45	11.359%	$272.2171	$272.22	$272.20	$272.20
7 purchase totals =	$734.49		$794.3233	$794.33	$794.30	$794.30