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	$162.43	5.298%	$171.0355	$171.04	$171.05	$171.00
Purchase #2	$62.42	12.397%	$70.1582	$70.16	$70.15	$70.20
Purchase #3	$240.81	8.454%	$261.1681	$261.17	$261.15	$261.20
Purchase #4	$35.56	10.750%	$39.3827	$39.38	$39.40	$39.40
Purchase #5	$207.69	11.256%	$231.0676	$231.07	$231.05	$231.10
Purchase #6	$73.41	13.225%	$83.1185	$83.12	$83.10	$83.10
Purchase #7	$232.78	7.782%	$250.8949	$250.89	$250.90	$250.90
7 purchase totals =	$1,015.10		$1,106.8255	$1,106.83	$1,106.80	$1,106.90