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	$152.47	10.203%	$168.0265	$168.03	$168.05	$168.00
Purchase #2	$94.63	11.445%	$105.4604	$105.46	$105.45	$105.50
Purchase #3	$138.46	10.328%	$152.7601	$152.76	$152.75	$152.80
Purchase #4	$49.58	12.236%	$55.6466	$55.65	$55.65	$55.60
Purchase #5	$181.55	5.465%	$191.4717	$191.47	$191.45	$191.50
Purchase #6	$80.53	6.821%	$86.023	$86.02	$86.00	$86.00
Purchase #7	$230.33	12.110%	$258.223	$258.22	$258.20	$258.20
7 purchase totals =	$927.55		$1,017.6113	$1,017.61	$1,017.55	$1,017.60