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	$200.85	10.300%	$221.5376	$221.54	$221.55	$221.50
Purchase #2	$86.50	11.842%	$96.7433	$96.74	$96.75	$96.70
Purchase #3	$169.46	5.297%	$178.4363	$178.44	$178.45	$178.40
Purchase #4	$135.45	10.512%	$149.6885	$149.69	$149.70	$149.70
Purchase #5	$218.58	8.621%	$237.4238	$237.42	$237.40	$237.40
Purchase #6	$144.96	13.671%	$164.7775	$164.78	$164.80	$164.80
Purchase #7	$72.49	8.321%	$78.5219	$78.52	$78.50	$78.50
7 purchase totals =	$1,028.29		$1,127.1289	$1,127.13	$1,127.15	$1,127.00