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	$181.97	9.584%	$199.41	$199.41	$199.40	$199.40
Purchase #2	$158.94	3.653%	$164.7461	$164.75	$164.75	$164.70
Purchase #3	$89.60	7.573%	$96.3854	$96.39	$96.40	$96.40
Purchase #4	$157.75	8.647%	$171.3906	$171.39	$171.40	$171.40
Purchase #5	$248.94	6.554%	$265.2555	$265.26	$265.25	$265.30
Purchase #6	$80.53	12.568%	$90.651	$90.65	$90.65	$90.70
Purchase #7	$149.47	11.329%	$166.4035	$166.40	$166.40	$166.40
7 purchase totals =	$1,067.20		$1,154.2421	$1,154.25	$1,154.25	$1,154.30