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	$131.79	7.863%	$142.1526	$142.15	$142.15	$142.20
Purchase #2	$57.26	13.280%	$64.8641	$64.86	$64.85	$64.90
Purchase #3	$168.41	11.282%	$187.41	$187.41	$187.40	$187.40
Purchase #4	$51.42	4.566%	$53.7678	$53.77	$53.75	$53.80
Purchase #5	$50.86	4.619%	$53.2092	$53.21	$53.20	$53.20
Purchase #6	$61.44	4.292%	$64.077	$64.08	$64.10	$64.10
Purchase #7	$114.99	10.771%	$127.3756	$127.38	$127.40	$127.40
7 purchase totals =	$636.17		$692.8563	$692.86	$692.85	$693.00