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	$157.44	9.674%	$172.6707	$172.67	$172.65	$172.70
Purchase #2	$47.60	4.662%	$49.8191	$49.82	$49.80	$49.80
Purchase #3	$240.76	9.337%	$263.2398	$263.24	$263.25	$263.20
Purchase #4	$165.59	11.758%	$185.0601	$185.06	$185.05	$185.10
Purchase #5	$186.34	4.351%	$194.4477	$194.45	$194.45	$194.40
Purchase #6	$96.25	7.695%	$103.6564	$103.66	$103.65	$103.70
Purchase #7	$160.91	9.660%	$176.4539	$176.45	$176.45	$176.50
7 purchase totals =	$1,054.89		$1,145.3477	$1,145.35	$1,145.30	$1,145.40