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	$98.71	4.677%	$103.3267	$103.33	$103.35	$103.30
Purchase #2	$179.25	3.730%	$185.936	$185.94	$185.95	$185.90
Purchase #3	$89.97	7.348%	$96.581	$96.58	$96.60	$96.60
Purchase #4	$201.67	9.753%	$221.3389	$221.34	$221.35	$221.30
Purchase #5	$90.56	6.839%	$96.7534	$96.75	$96.75	$96.80
Purchase #6	$156.73	9.256%	$171.2369	$171.24	$171.25	$171.20
Purchase #7	$216.27	6.558%	$230.453	$230.45	$230.45	$230.50
7 purchase totals =	$1,033.16		$1,105.6259	$1,105.63	$1,105.70	$1,105.60