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	$106.53	5.396%	$112.2784	$112.28	$112.30	$112.30
Purchase #2	$178.25	10.234%	$196.4921	$196.49	$196.50	$196.50
Purchase #3	$104.85	5.298%	$110.405	$110.41	$110.40	$110.40
Purchase #4	$20.77	3.417%	$21.4797	$21.48	$21.50	$21.50
Purchase #5	$115.42	13.524%	$131.0294	$131.03	$131.05	$131.00
Purchase #6	$164.27	6.158%	$174.3857	$174.39	$174.40	$174.40
Purchase #7	$193.55	4.698%	$202.643	$202.64	$202.65	$202.60
7 purchase totals =	$883.64		$948.7133	$948.72	$948.80	$948.70