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	$72.31	9.656%	$79.2923	$79.29	$79.30	$79.30
Purchase #2	$176.33	5.138%	$185.3898	$185.39	$185.40	$185.40
Purchase #3	$39.27	12.621%	$44.2263	$44.23	$44.25	$44.20
Purchase #4	$69.59	3.547%	$72.0584	$72.06	$72.05	$72.10
Purchase #5	$64.94	5.254%	$68.3519	$68.35	$68.35	$68.40
Purchase #6	$196.69	4.386%	$205.3168	$205.32	$205.30	$205.30
Purchase #7	$112.46	5.756%	$118.9332	$118.93	$118.95	$118.90
7 purchase totals =	$731.59		$773.5687	$773.57	$773.60	$773.60