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	$166.73	5.813%	$176.422	$176.42	$176.40	$176.40
Purchase #2	$91.46	8.111%	$98.8783	$98.88	$98.90	$98.90
Purchase #3	$12.93	12.712%	$14.5737	$14.57	$14.55	$14.60
Purchase #4	$5.78	8.588%	$6.2764	$6.28	$6.30	$6.30
Purchase #5	$135.33	4.551%	$141.4889	$141.49	$141.50	$141.50
Purchase #6	$169.41	9.513%	$185.526	$185.53	$185.55	$185.50
Purchase #7	$243.91	5.206%	$256.608	$256.61	$256.60	$256.60
7 purchase totals =	$825.55		$879.7733	$879.78	$879.80	$879.80