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	$237.73	5.520%	$250.8527	$250.85	$250.85	$250.90
Purchase #2	$249.27	13.564%	$283.081	$283.08	$283.10	$283.10
Purchase #3	$91.64	13.616%	$104.1177	$104.12	$104.10	$104.10
Purchase #4	$177.65	3.744%	$184.3012	$184.30	$184.30	$184.30
Purchase #5	$62.86	13.811%	$71.5416	$71.54	$71.55	$71.50
Purchase #6	$201.83	4.793%	$211.5037	$211.50	$211.50	$211.50
Purchase #7	$134.31	11.682%	$150.0001	$150.00	$150.00	$150.00
7 purchase totals =	$1,155.29		$1,255.3980	$1,255.39	$1,255.40	$1,255.40