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	$190.83	4.321%	$199.0758	$199.08	$199.10	$199.10
Purchase #2	$53.53	12.558%	$60.2523	$60.25	$60.25	$60.30
Purchase #3	$244.48	6.300%	$259.8822	$259.88	$259.90	$259.90
Purchase #4	$158.64	5.812%	$167.8602	$167.86	$167.85	$167.90
Purchase #5	$228.91	13.266%	$259.2772	$259.28	$259.30	$259.30
Purchase #6	$190.33	13.194%	$215.4421	$215.44	$215.45	$215.40
Purchase #7	$76.52	5.407%	$80.6574	$80.66	$80.65	$80.70
7 purchase totals =	$1,143.24		$1,242.4472	$1,242.45	$1,242.50	$1,242.60