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	$134.82	6.262%	$143.2624	$143.26	$143.25	$143.30
Purchase #2	$74.75	10.272%	$82.4283	$82.43	$82.45	$82.40
Purchase #3	$242.94	10.508%	$268.4681	$268.47	$268.45	$268.50
Purchase #4	$50.90	10.543%	$56.2664	$56.27	$56.25	$56.30
Purchase #5	$211.53	9.856%	$232.3784	$232.38	$232.40	$232.40
Purchase #6	$180.75	7.394%	$194.1147	$194.11	$194.10	$194.10
Purchase #7	$78.44	8.333%	$84.9764	$84.98	$85.00	$85.00
7 purchase totals =	$974.13		$1,061.8947	$1,061.90	$1,061.90	$1,062.00