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	$153.59	13.767%	$174.7347	$174.73	$174.75	$174.70
Purchase #2	$227.61	4.528%	$237.9162	$237.92	$237.90	$237.90
Purchase #3	$166.32	5.281%	$175.1034	$175.10	$175.10	$175.10
Purchase #4	$89.71	13.167%	$101.5221	$101.52	$101.50	$101.50
Purchase #5	$51.60	3.137%	$53.2187	$53.22	$53.20	$53.20
Purchase #6	$137.83	12.752%	$155.4061	$155.41	$155.40	$155.40
Purchase #7	$85.64	12.661%	$96.4829	$96.48	$96.50	$96.50
7 purchase totals =	$912.30		$994.3841	$994.38	$994.35	$994.30