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	$71.92	9.340%	$78.6373	$78.64	$78.65	$78.60
Purchase #2	$236.55	3.690%	$245.2787	$245.28	$245.30	$245.30
Purchase #3	$104.50	13.469%	$118.5751	$118.58	$118.60	$118.60
Purchase #4	$166.89	7.609%	$179.5887	$179.59	$179.60	$179.60
Purchase #5	$216.41	5.505%	$228.3234	$228.32	$228.30	$228.30
Purchase #6	$135.78	6.583%	$144.7184	$144.72	$144.70	$144.70
Purchase #7	$97.64	13.243%	$110.5705	$110.57	$110.55	$110.60
7 purchase totals =	$1,029.69		$1,105.6921	$1,105.70	$1,105.70	$1,105.70