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	$244.61	3.742%	$253.7633	$253.76	$253.75	$253.80
Purchase #2	$204.27	5.676%	$215.8644	$215.86	$215.85	$215.90
Purchase #3	$142.42	7.150%	$152.603	$152.60	$152.60	$152.60
Purchase #4	$144.54	12.459%	$162.5482	$162.55	$162.55	$162.50
Purchase #5	$62.29	9.631%	$68.2891	$68.29	$68.30	$68.30
Purchase #6	$93.37	7.702%	$100.5614	$100.56	$100.55	$100.60
Purchase #7	$49.36	3.245%	$50.9617	$50.96	$50.95	$51.00
7 purchase totals =	$940.86		$1,004.5911	$1,004.58	$1,004.55	$1,004.70