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	$167.87	8.449%	$182.0533	$182.05	$182.05	$182.10
Purchase #2	$25.64	11.164%	$28.5024	$28.50	$28.50	$28.50
Purchase #3	$164.89	6.167%	$175.0588	$175.06	$175.05	$175.10
Purchase #4	$118.71	8.292%	$128.5534	$128.55	$128.55	$128.60
Purchase #5	$141.82	10.365%	$156.5196	$156.52	$156.50	$156.50
Purchase #6	$123.38	6.631%	$131.5613	$131.56	$131.55	$131.60
Purchase #7	$41.99	9.113%	$45.8165	$45.82	$45.80	$45.80
7 purchase totals =	$784.30		$848.0653	$848.06	$848.00	$848.20