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	$8.48	3.608%	$8.786	$8.79	$8.80	$8.80
Purchase #2	$221.89	10.533%	$245.2617	$245.26	$245.25	$245.30
Purchase #3	$174.44	7.467%	$187.4654	$187.47	$187.45	$187.50
Purchase #4	$61.44	8.811%	$66.8535	$66.85	$66.85	$66.90
Purchase #5	$240.52	9.492%	$263.3502	$263.35	$263.35	$263.40
Purchase #6	$174.54	9.106%	$190.4336	$190.43	$190.45	$190.40
Purchase #7	$6.96	6.423%	$7.407	$7.41	$7.40	$7.40
7 purchase totals =	$888.27		$969.5574	$969.56	$969.55	$969.70