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	$127.79	5.442%	$134.7443	$134.74	$134.75	$134.70
Purchase #2	$203.61	7.472%	$218.8237	$218.82	$218.80	$218.80
Purchase #3	$166.65	12.801%	$187.9829	$187.98	$188.00	$188.00
Purchase #4	$223.61	9.801%	$245.526	$245.53	$245.55	$245.50
Purchase #5	$126.35	12.850%	$142.586	$142.59	$142.60	$142.60
Purchase #6	$94.98	12.483%	$106.8364	$106.84	$106.85	$106.80
Purchase #7	$10.33	4.249%	$10.7689	$10.77	$10.75	$10.80
7 purchase totals =	$953.32		$1,047.2682	$1,047.27	$1,047.30	$1,047.20