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	$166.56	9.360%	$182.15	$182.15	$182.15	$182.20
Purchase #2	$199.75	3.341%	$206.4236	$206.42	$206.40	$206.40
Purchase #3	$90.91	13.810%	$103.4647	$103.46	$103.45	$103.50
Purchase #4	$49.83	5.277%	$52.4595	$52.46	$52.45	$52.50
Purchase #5	$203.93	12.176%	$228.7605	$228.76	$228.75	$228.80
Purchase #6	$245.84	3.199%	$253.7044	$253.70	$253.70	$253.70
Purchase #7	$145.56	4.478%	$152.0782	$152.08	$152.10	$152.10
7 purchase totals =	$1,102.38		$1,179.0409	$1,179.03	$1,179.00	$1,179.20