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	$188.29	3.312%	$194.5262	$194.53	$194.55	$194.50
Purchase #2	$200.44	9.386%	$219.2533	$219.25	$219.25	$219.30
Purchase #3	$38.94	8.798%	$42.3659	$42.37	$42.35	$42.40
Purchase #4	$105.47	6.794%	$112.6356	$112.64	$112.65	$112.60
Purchase #5	$61.93	5.464%	$65.3139	$65.31	$65.30	$65.30
Purchase #6	$162.57	6.604%	$173.3061	$173.31	$173.30	$173.30
Purchase #7	$25.82	9.428%	$28.2543	$28.25	$28.25	$28.30
7 purchase totals =	$783.46		$835.6553	$835.66	$835.65	$835.70