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	$147.60	4.499%	$154.2405	$154.24	$154.25	$154.20
Purchase #2	$139.25	12.470%	$156.6145	$156.61	$156.60	$156.60
Purchase #3	$174.96	7.798%	$188.6034	$188.60	$188.60	$188.60
Purchase #4	$104.38	3.222%	$107.7431	$107.74	$107.75	$107.70
Purchase #5	$150.41	10.772%	$166.6122	$166.61	$166.60	$166.60
Purchase #6	$34.77	10.393%	$38.3836	$38.38	$38.40	$38.40
Purchase #7	$156.91	3.801%	$162.8741	$162.87	$162.85	$162.90
7 purchase totals =	$908.28		$975.0714	$975.05	$975.05	$975.00