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	$81.80	6.225%	$86.8921	$86.89	$86.90	$86.90
Purchase #2	$42.49	4.288%	$44.312	$44.31	$44.30	$44.30
Purchase #3	$240.40	7.553%	$258.5574	$258.56	$258.55	$258.60
Purchase #4	$99.38	13.166%	$112.4644	$112.46	$112.45	$112.50
Purchase #5	$205.50	13.491%	$233.224	$233.22	$233.20	$233.20
Purchase #6	$181.68	5.428%	$191.5416	$191.54	$191.55	$191.50
Purchase #7	$90.62	6.216%	$96.2529	$96.25	$96.25	$96.30
7 purchase totals =	$941.87		$1,023.2444	$1,023.23	$1,023.20	$1,023.30