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	$230.37	4.414%	$240.5385	$240.54	$240.55	$240.50
Purchase #2	$154.56	8.853%	$168.2432	$168.24	$168.25	$168.20
Purchase #3	$193.27	10.370%	$213.3121	$213.31	$213.30	$213.30
Purchase #4	$110.75	3.705%	$114.8533	$114.85	$114.85	$114.90
Purchase #5	$236.46	11.370%	$263.3455	$263.35	$263.35	$263.30
Purchase #6	$59.31	8.609%	$64.416	$64.42	$64.40	$64.40
Purchase #7	$19.42	10.843%	$21.5257	$21.53	$21.55	$21.50
7 purchase totals =	$1,004.14		$1,086.2343	$1,086.24	$1,086.25	$1,086.10