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	$91.30	13.104%	$103.264	$103.26	$103.25	$103.30
Purchase #2	$240.92	11.392%	$268.3656	$268.37	$268.35	$268.40
Purchase #3	$202.53	6.352%	$215.3947	$215.39	$215.40	$215.40
Purchase #4	$117.28	5.318%	$123.517	$123.52	$123.50	$123.50
Purchase #5	$146.47	9.431%	$160.2836	$160.28	$160.30	$160.30
Purchase #6	$110.55	3.167%	$114.0511	$114.05	$114.05	$114.10
Purchase #7	$29.92	10.298%	$33.0012	$33.00	$33.00	$33.00
7 purchase totals =	$938.97		$1,017.8772	$1,017.87	$1,017.85	$1,018.00