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	$218.73	8.735%	$237.8361	$237.84	$237.85	$237.80
Purchase #2	$250.48	7.212%	$268.5446	$268.54	$268.55	$268.50
Purchase #3	$57.83	8.183%	$62.5622	$62.56	$62.55	$62.60
Purchase #4	$111.73	10.112%	$123.0281	$123.03	$123.05	$123.00
Purchase #5	$156.65	3.595%	$162.2816	$162.28	$162.30	$162.30
Purchase #6	$153.91	8.485%	$166.9693	$166.97	$166.95	$167.00
Purchase #7	$6.80	7.735%	$7.326	$7.33	$7.35	$7.30
7 purchase totals =	$956.13		$1,028.5479	$1,028.55	$1,028.60	$1,028.50