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	$153.44	10.695%	$169.8504	$169.85	$169.85	$169.90
Purchase #2	$53.89	10.266%	$59.4223	$59.42	$59.40	$59.40
Purchase #3	$41.34	4.714%	$43.2888	$43.29	$43.30	$43.30
Purchase #4	$105.90	10.671%	$117.2006	$117.20	$117.20	$117.20
Purchase #5	$200.41	6.211%	$212.8575	$212.86	$212.85	$212.90
Purchase #6	$187.58	4.728%	$196.4488	$196.45	$196.45	$196.40
Purchase #7	$199.54	4.381%	$208.2818	$208.28	$208.30	$208.30
7 purchase totals =	$942.10		$1,007.3502	$1,007.35	$1,007.35	$1,007.40