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	$53.25	11.225%	$59.2273	$59.23	$59.25	$59.20
Purchase #2	$180.28	11.152%	$200.3848	$200.38	$200.40	$200.40
Purchase #3	$71.30	5.299%	$75.0782	$75.08	$75.10	$75.10
Purchase #4	$33.30	11.641%	$37.1765	$37.18	$37.20	$37.20
Purchase #5	$175.55	6.518%	$186.9923	$186.99	$187.00	$187.00
Purchase #6	$62.60	10.228%	$69.0027	$69.00	$69.00	$69.00
Purchase #7	$56.38	9.526%	$61.7508	$61.75	$61.75	$61.80
7 purchase totals =	$632.66		$689.6126	$689.61	$689.70	$689.70