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	$151.27	10.345%	$166.9189	$166.92	$166.90	$166.90
Purchase #2	$38.27	6.136%	$40.6182	$40.62	$40.60	$40.60
Purchase #3	$57.88	6.102%	$61.4118	$61.41	$61.40	$61.40
Purchase #4	$242.46	7.407%	$260.419	$260.42	$260.40	$260.40
Purchase #5	$101.55	4.520%	$106.1401	$106.14	$106.15	$106.10
Purchase #6	$127.53	9.372%	$139.4821	$139.48	$139.50	$139.50
Purchase #7	$231.82	11.190%	$257.7607	$257.76	$257.75	$257.80
7 purchase totals =	$950.78		$1,032.7508	$1,032.75	$1,032.70	$1,032.70