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	$142.86	6.350%	$151.9316	$151.93	$151.95	$151.90
Purchase #2	$233.53	3.844%	$242.5069	$242.51	$242.50	$242.50
Purchase #3	$183.79	6.661%	$196.0323	$196.03	$196.05	$196.00
Purchase #4	$39.27	4.490%	$41.0332	$41.03	$41.05	$41.00
Purchase #5	$83.94	7.348%	$90.1079	$90.11	$90.10	$90.10
Purchase #6	$74.96	3.843%	$77.8407	$77.84	$77.85	$77.80
Purchase #7	$98.25	3.844%	$102.0267	$102.03	$102.05	$102.00
7 purchase totals =	$856.60		$901.4793	$901.48	$901.55	$901.30