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	$246.41	3.522%	$255.0886	$255.09	$255.10	$255.10
Purchase #2	$162.51	3.673%	$168.479	$168.48	$168.50	$168.50
Purchase #3	$144.48	5.260%	$152.0796	$152.08	$152.10	$152.10
Purchase #4	$37.72	7.270%	$40.4622	$40.46	$40.45	$40.50
Purchase #5	$191.95	4.566%	$200.7144	$200.71	$200.70	$200.70
Purchase #6	$92.60	4.383%	$96.6587	$96.66	$96.65	$96.70
Purchase #7	$167.91	10.281%	$185.1728	$185.17	$185.15	$185.20
7 purchase totals =	$1,043.58		$1,098.6553	$1,098.65	$1,098.65	$1,098.80