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	$144.39	12.626%	$162.6207	$162.62	$162.60	$162.60
Purchase #2	$245.31	9.577%	$268.8033	$268.80	$268.80	$268.80
Purchase #3	$161.43	4.285%	$168.3473	$168.35	$168.35	$168.30
Purchase #4	$187.32	9.600%	$205.3027	$205.30	$205.30	$205.30
Purchase #5	$39.41	4.789%	$41.2973	$41.30	$41.30	$41.30
Purchase #6	$87.28	13.647%	$99.1911	$99.19	$99.20	$99.20
Purchase #7	$236.80	11.436%	$263.8804	$263.88	$263.90	$263.90
7 purchase totals =	$1,101.94		$1,209.4428	$1,209.44	$1,209.45	$1,209.40