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	$100.83	4.602%	$105.4702	$105.47	$105.45	$105.50
Purchase #2	$225.53	6.663%	$240.5571	$240.56	$240.55	$240.60
Purchase #3	$30.79	3.263%	$31.7947	$31.79	$31.80	$31.80
Purchase #4	$158.43	11.160%	$176.1108	$176.11	$176.10	$176.10
Purchase #5	$82.63	4.609%	$86.4384	$86.44	$86.45	$86.40
Purchase #6	$153.62	4.651%	$160.7649	$160.76	$160.75	$160.80
Purchase #7	$35.71	13.799%	$40.6376	$40.64	$40.65	$40.60
7 purchase totals =	$787.54		$841.7737	$841.77	$841.75	$841.80