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	$178.78	10.137%	$196.9029	$196.90	$196.90	$196.90
Purchase #2	$127.56	5.844%	$135.0146	$135.01	$135.00	$135.00
Purchase #3	$100.56	6.154%	$106.7485	$106.75	$106.75	$106.70
Purchase #4	$8.39	6.320%	$8.9202	$8.92	$8.90	$8.90
Purchase #5	$174.59	3.606%	$180.8857	$180.89	$180.90	$180.90
Purchase #6	$202.29	10.565%	$223.6619	$223.66	$223.65	$223.70
Purchase #7	$28.57	11.689%	$31.9095	$31.91	$31.90	$31.90
7 purchase totals =	$820.74		$884.0433	$884.04	$884.00	$884.00