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	$178.99	4.765%	$187.5189	$187.52	$187.50	$187.50
Purchase #2	$209.84	4.387%	$219.0457	$219.05	$219.05	$219.00
Purchase #3	$79.57	3.210%	$82.1242	$82.12	$82.10	$82.10
Purchase #4	$73.28	11.404%	$81.6369	$81.64	$81.65	$81.60
Purchase #5	$187.35	4.658%	$196.0768	$196.08	$196.10	$196.10
Purchase #6	$144.56	9.485%	$158.2715	$158.27	$158.25	$158.30
Purchase #7	$164.43	4.523%	$171.8672	$171.87	$171.85	$171.90
7 purchase totals =	$1,038.02		$1,096.5412	$1,096.55	$1,096.50	$1,096.50