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	$172.98	9.602%	$189.5895	$189.59	$189.60	$189.60
Purchase #2	$115.52	10.490%	$127.638	$127.64	$127.65	$127.60
Purchase #3	$195.72	11.711%	$218.6408	$218.64	$218.65	$218.60
Purchase #4	$77.76	7.186%	$83.3478	$83.35	$83.35	$83.30
Purchase #5	$80.59	7.661%	$86.764	$86.76	$86.75	$86.80
Purchase #6	$243.52	4.439%	$254.3299	$254.33	$254.35	$254.30
Purchase #7	$207.86	10.684%	$230.0678	$230.07	$230.05	$230.10
7 purchase totals =	$1,093.95		$1,190.3778	$1,190.38	$1,190.40	$1,190.30