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	$160.79	8.295%	$174.1275	$174.13	$174.15	$174.10
Purchase #2	$92.82	8.464%	$100.6763	$100.68	$100.70	$100.70
Purchase #3	$213.98	7.815%	$230.7025	$230.70	$230.70	$230.70
Purchase #4	$39.83	7.533%	$42.8304	$42.83	$42.85	$42.80
Purchase #5	$135.78	13.814%	$154.5366	$154.54	$154.55	$154.50
Purchase #6	$149.96	9.626%	$164.3951	$164.40	$164.40	$164.40
Purchase #7	$72.45	13.715%	$82.3865	$82.39	$82.40	$82.40
7 purchase totals =	$865.61		$949.6549	$949.67	$949.75	$949.60