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	$31.54	13.612%	$35.8332	$35.83	$35.85	$35.80
Purchase #2	$26.41	9.422%	$28.8984	$28.90	$28.90	$28.90
Purchase #3	$173.45	5.279%	$182.6064	$182.61	$182.60	$182.60
Purchase #4	$161.60	8.255%	$174.9401	$174.94	$174.95	$174.90
Purchase #5	$152.69	6.298%	$162.3064	$162.31	$162.30	$162.30
Purchase #6	$41.59	7.214%	$44.5903	$44.59	$44.60	$44.60
Purchase #7	$134.90	11.611%	$150.5632	$150.56	$150.55	$150.60
7 purchase totals =	$722.18		$779.7380	$779.74	$779.75	$779.70