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	$65.38	11.478%	$72.8843	$72.88	$72.90	$72.90
Purchase #2	$214.67	7.798%	$231.41	$231.41	$231.40	$231.40
Purchase #3	$17.34	7.413%	$18.6254	$18.63	$18.65	$18.60
Purchase #4	$159.39	7.477%	$171.3076	$171.31	$171.30	$171.30
Purchase #5	$86.38	4.469%	$90.2403	$90.24	$90.25	$90.20
Purchase #6	$145.88	4.653%	$152.6678	$152.67	$152.65	$152.70
Purchase #7	$241.41	11.211%	$268.4745	$268.47	$268.45	$268.50
7 purchase totals =	$930.45		$1,005.6099	$1,005.61	$1,005.60	$1,005.60