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	$174.87	7.174%	$187.4152	$187.42	$187.40	$187.40
Purchase #2	$78.26	13.834%	$89.0865	$89.09	$89.10	$89.10
Purchase #3	$41.64	4.328%	$43.4422	$43.44	$43.45	$43.40
Purchase #4	$144.80	7.730%	$155.993	$155.99	$156.00	$156.00
Purchase #5	$108.29	10.252%	$119.3919	$119.39	$119.40	$119.40
Purchase #6	$79.96	4.169%	$83.2935	$83.29	$83.30	$83.30
Purchase #7	$148.63	12.114%	$166.635	$166.64	$166.65	$166.60
7 purchase totals =	$776.45		$845.2573	$845.26	$845.30	$845.20