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	$40.92	7.192%	$43.863	$43.86	$43.85	$43.90
Purchase #2	$106.48	8.132%	$115.139	$115.14	$115.15	$115.10
Purchase #3	$82.56	12.128%	$92.5729	$92.57	$92.55	$92.60
Purchase #4	$228.77	9.328%	$250.1097	$250.11	$250.10	$250.10
Purchase #5	$166.37	10.760%	$184.2714	$184.27	$184.25	$184.30
Purchase #6	$38.36	10.833%	$42.5155	$42.52	$42.50	$42.50
Purchase #7	$157.67	11.818%	$176.3034	$176.30	$176.30	$176.30
7 purchase totals =	$821.13		$904.7749	$904.77	$904.70	$904.80